Cohabitation vs Marriage - What the Evidence Says
In brief: There's no such thing as common-law marriage. Nearly half the people of England and Wales believe that living together long enough gives a couple the rights of a married couple. In law it doesn't. https://committees.parliament.uk/publications/23321/documents/170094/default/ A cohabiting partner has no automatic claim on the home, faces inheritance tax that a husband or wife wouldn't pay and, if the other dies without a will, has no automatic right to inherit anything and can't even apply to administer the estate. https://www.gov.uk/government/consultations/a-fairer-end-to-relationships/a-fairer-end-to-relationships-consultation-document https://committees.parliament.uk/publications/23321/documents/170094/default/ The relational evidence is no kinder. Cohabiting parents are 3.4 times as likely as married parents to split up in any year, and more likely to split up in every income band. https://marriagefoundation.org.uk/research/married-poor-more-stable-than-unmarried-rich/ Millions of families are banking on protections they don't have. In June 2026 the Government proposed giving cohabiting couples who qualify a spouse's inheritance rights when a partner dies without a will, and new financial claims when they separate - marriage by another name. https://www.gov.uk/government/consultations/a-fairer-end-to-relationships/a-fairer-end-to-relationships-consultation-document Finland's narrower law of 2011 was followed by substantial falls in marriage and fertility. https://www.centreforsocialjustice.org.uk/library/finnishing-marriage
ON THIS PAGE
- The scale of it
- The myth that leaves families exposed
- What cohabiting couples don't have
- The Government's answer - and why it's wrong
- The stability gap
- Sliding versus deciding
- What it means for children
- Selection or causation?
- Even where living together is the norm
- If you're cohabiting now
- What we believe
- Related pages on c4m.org.uk
- Key sources
THE SCALE OF IT
Unmarried cohabiting-couple families numbered 3.5 million in 2025 - 17.6 per cent of all UK families. The overwhelming majority - 95.1 per cent - are couples of the opposite sex. https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/families/bulletins/familiesandhouseholds/2025 Married couples of a man and a woman made up 64.7 per cent of families, down from 66.5 per cent in 2015. Yet in number they grew by almost 400,000 over those ten years, more than any other kind of family. https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/families/datasets/familiesandhouseholdsfamiliesandhouseholds
Among the young the retreat from marriage is dramatic. Of women born in 1946, 81 per cent had married by their 25th birthday, against 4 per cent of those born in 1998. https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/marriagecohabitationandcivilpartnerships/datasets/marriagesinenglandandwales2013 The Centre for Social Justice's report I Do?, published in February 2026, found that the marriage rate for women aged 20 to 24 had fallen 97 per cent since 1972. Among couples living together in their late twenties, married or not, the share who are unmarried rose from 56 to 72 per cent between 2011 and 2021. https://www.centreforsocialjustice.org.uk/wp-content/uploads/2026/02/CSJ-I_Do.pdf
The question is whether the people in those 3.5 million families know what the law actually gives them, and what the evidence says about the road they're on. https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/families/bulletins/familiesandhouseholds/2025 On both counts, millions don't.
THE MYTH THAT LEAVES FAMILIES EXPOSED
The British Social Attitudes Survey of 2019 found that 46 per cent of people in England and Wales believe cohabiting couples form a "common law marriage" with the same legal rights as married couples. Among households with children, it's 55 per cent. https://news-archive.exeter.ac.uk/2019/january/title_700858_en.html The belief has barely moved in fourteen years. It stood at 47 per cent in 2005, according to the University of Exeter in 2019. https://news-archive.exeter.ac.uk/2019/january/title_700858_en.html
Professor Anne Barlow of the University of Exeter said, "Our data clearly show that almost half of us falsely believe that common law marriage exists in England and Wales when, in reality, cohabitation grants no general legal status to a couple." https://news-archive.exeter.ac.uk/2019/january/title_700858_en.html
The households most likely to believe the myth are the ones with children - the households with most to lose. https://news-archive.exeter.ac.uk/2019/january/title_700858_en.html A couple who believe they're protected see no need to make wills, check the property title or fill in the pension nomination form. They find out the truth at the worst possible moment, at a death or a break-up.
WHAT COHABITING COUPLES DON'T HAVE
THE HOME
A cohabiting partner has no automatic right to the home. If the house is in the other's name, the law gives no claim on separation unless a beneficial interest can be proved through the courts - complex, very expensive and time consuming. https://committees.parliament.uk/publications/23321/documents/170094/default/ https://www.gov.uk/government/consultations/a-fairer-end-to-relationships/a-fairer-end-to-relationships-consultation-document A wife or husband can register "home rights" that help stop the other selling the home, and can usually go on living there until the divorce is settled. https://www.gov.uk/stay-in-home-during-separation-or-divorce And the divorce courts can share out property between spouses under the Matrimonial Causes Act 1973. https://www.gov.uk/government/consultations/a-fairer-end-to-relationships/a-fairer-end-to-relationships-consultation-document A cohabiting partner who paid towards the mortgage for twenty years must still go to court to prove a share of the home.
INHERITANCE
Die without a will and your cohabiting partner has no automatic right to inherit anything. https://www.gov.uk/inherits-someone-dies-without-will The intestacy rules of England and Wales pass the estate to children, parents or siblings - not to the person you shared your life with. The survivor can apply to the court under the Inheritance (Provision for Family and Dependants) Act 1975, but that's a costly and uncertain claim made in the middle of grief. https://www.gov.uk/government/consultations/a-fairer-end-to-relationships/a-fairer-end-to-relationships-consultation-document A widowed husband or wife inherits automatically, and inherits everything if there are no children or other descendants. https://www.gov.uk/inherits-someone-dies-without-will
INHERITANCE TAX
A husband or wife can leave everything to the other free of inheritance tax. https://www.gov.uk/inheritance-tax Each spouse's tax-free threshold can rise to £500,000 where the family home goes to children or grandchildren and the estate is worth less than £2 million. https://www.gov.uk/inheritance-tax/passing-on-home The survivor inherits whatever threshold the first to die didn't use, so a married couple can pass on up to £1 million (£500,000 each) tax-free. https://www.gov.uk/inheritance-tax Between cohabiting partners there's no such exemption. Everything above £325,000 can be taxed at 40 per cent, including the home the survivor lives in. https://www.gov.uk/inheritance-tax
PENSIONS
In pensions law a husband or wife counts as a dependant automatically. In HM Revenue and Customs' words, "An individual married to, or a civil partner of, the member on the date the member died is a dependant." https://www.gov.uk/hmrc-internal-manuals/pensions-tax-manual/ptm071200 An unmarried partner counts only if the scheme accepts they depended on the member financially or through physical or mental impairment, or that the two of them depended on each other financially, and what a scheme pays still turns on its own rules. https://www.gov.uk/hmrc-internal-manuals/pensions-tax-manual/ptm071200 Many pension providers ask members to name the people they want to benefit on an expression of wish form, which a couple who think they're already protected see no reason to fill in. https://www.moneyhelper.org.uk/en/family-and-care/death-and-bereavement/putting-your-financial-affairs-in-order-if-you-get-ill-or-die-making-a-will-and-more The State Pension can pass in part to a widowed spouse, but every route to it needs a marriage or civil partnership. https://www.gov.uk/new-state-pension/inheriting-or-increasing-state-pension-from-a-spouse-or-civil-partner
NEXT OF KIN
"Next of kin" has no legal status in English law, and for medical purposes a patient can name anyone. https://www.uhs.nhs.uk/health-professionals/clinical-law-updates/is-there-a-role-for-next-of-kin Being named next of kin gives no power to decide anything for a patient who has lost capacity. A Lasting Power of Attorney gives the person you appoint "powers entirely unavailable to the next of kin". https://www.uhs.nhs.uk/health-professionals/clinical-law-updates/is-there-a-role-for-next-of-kin
Where the law does favour the spouse is after death. In the Government's own words, when someone dies without a will, "cohabitants have no standing to apply for such a grant" to administer the estate. So a partner of 30 years must stand aside while a parent, child or sibling takes charge, where a husband or wife would come first. https://www.gov.uk/government/consultations/a-fairer-end-to-relationships/a-fairer-end-to-relationships-consultation-document
FATHERS
A father not married to his child's mother doesn't automatically hold parental responsibility. In England and Wales, since 1 December 2003, he acquires it by being registered on the birth certificate jointly with the mother. https://www.legislation.gov.uk/ukpga/2002/38/section/111 Unmarried fathers registered before December 2003, or not named, need an agreement or a court order, unless the birth is re-registered - jointly, or after they marry the mother. A married father has it from birth. https://www.gov.uk/government/publications/parental-responsibility-birth-parents-adoption-and-surrogacy-caseworker-guidance/parental-responsibility-birth-parents-adoption-and-surrogacy-accessible-version
TAX
The Marriage Allowance lets a married couple transfer £1,260 of personal allowance, worth up to £252 a year. Cohabiting couples can't claim it. https://www.gov.uk/marriage-allowance
All told, a couple who live together for 30 years believing they have a married couple's protections have almost none of them in law over the home, the estate, tax and pensions. https://committees.parliament.uk/publications/23321/documents/170094/default/
THE GOVERNMENT'S ANSWER - AND WHY IT'S WRONG
Those legal gaps are now live politics. On 5 June 2026 the Ministry of Justice opened a consultation, A fairer end to relationships, proposing, among other things, a new framework of separation rights for eligible cohabitants and, on intestacy, inheritance rights identical to a spouse's. https://www.gov.uk/government/consultations/a-fairer-end-to-relationships/a-fairer-end-to-relationships-consultation-document It closed on 14 August 2026, and the Government's page still says "We are analysing your feedback". No response has been published. https://www.gov.uk/government/consultations/a-fairer-end-to-relationships
The Coalition for Marriage (C4M) responded with the case against treating cohabitation as marriage by another name. https://www.c4m.org.uk/storage/media/58/C4M-Response-A-Fairer-End-to-Relationships.pdf All our consultation responses are at https://www.c4m.org.uk/marriage-support/our-responses-to-consultations. The Government's own impact assessment puts the net cost of its main proposal for cohabitants at £39.1 million over ten years, and assumes about 6,700 financial claims a year between separating cohabitants. Yet by its own account, not one benefit can be given a money value. https://assets.publishing.service.gov.uk/media/6a1eee48050971fbebf3bd8b/Regulatory_Impact_Assessment_-_Cohabitation_and_Financial_Remedies_Reform_Consultation.pdf The Government's Family Test goes further. Resting on a study from 2006, it claims that cohabitation reform is "not expected to deter couples from marrying". https://www.gov.uk/government/consultations/a-fairer-end-to-relationships/the-family-test-a-fairer-end-to-relationships
What followed in Finland contradicts that claim. Finland brought in a narrower law of the same kind for cohabiting couples in 2011. https://www.centreforsocialjustice.org.uk/library/finnishing-marriage The Centre for Social Justice's report Finnishing Marriage?, published in August 2026, found that reforms designed to narrow the legal distinction between marriage and cohabitation "were followed by substantial falls in marriage and fertility, without evidence of offsetting gains in family stability". On its estimate, Finnish women's first marriage rate was 23 per cent lower within seven years than it would have been without the reform. https://www.centreforsocialjustice.org.uk/library/finnishing-marriage
The answer to the common-law myth isn't to make the myth true but to tell people the truth, and to strengthen the institution that already gives these protections.
C4M isn't alone. The Marriage Foundation calls the plan "both foolish and fundamentally flawed". https://marriagefoundation.org.uk/marriage-foundation-responds-to-foolish-government-plans-that-downgrade-marriage/ In 2021 it opposed giving cohabitants marriage-like rights automatically, and proposed instead a high-profile information campaign on the benefits of formal commitment. https://marriagefoundation.org.uk/should-cohabiting-couples-have-similar-legal-rights-to-married-couples/ The Christian Institute warns that the changes "would disincentivise marriage and encourage cohabitation". https://www.christian.org.uk/news/ci-govts-cohabitation-plans-could-have-gifted-millions-to-taylor-swift-ex/ Civitas's factsheet The Facts Behind Cohabitation opposed extending marriage's rights to cohabiting couples who separate. https://www.civitas.org.uk/content/files/cohabitation.pdf The Centre for Social Justice calls the proposals "marriage-lite". https://www.centreforsocialjustice.org.uk/newsroom/marriage-lite-plans-threaten-to-cut-births-by-over-75000-a-year-new-study-finds
THE STABILITY GAP
The legal differences are only half the story. The other half is what happens to the relationships themselves, and here the British data is deep and consistent.
Between 2009 and 2018, married parents with dependent children split up at 1.9 per cent a year, cohabiting parents at 6.5 per cent - 3.4 times the rate. https://marriagefoundation.org.uk/research/married-poor-more-stable-than-unmarried-rich/ Over a childhood the gap compounds. A June 2026 re-analysis of first-time parents in the Millennium Cohort Study, published by the Marriage Foundation with the Centre for Social Justice, used the full sample rather than the three quarters the Institute for Fiscal Studies had previously analysed. https://marriagefoundation.org.uk/wp-content/uploads/2026/06/PhD-The-Timing-of-Marriage_digital-1.pdf Once 27 differences between the couples, including income, education and ethnicity, were allowed for, the chance of separating by the child's 14th birthday was 45 per cent for parents who never married against 26 per cent for those who married before conception. Those differences left between half and two thirds of the original gap unexplained. https://marriagefoundation.org.uk/wp-content/uploads/2026/06/PhD-The-Timing-of-Marriage_digital-1.pdf
The obvious objection is that this is really about money, but the Marriage Foundation's 2022 study, which tested exactly that, found the gap present in all five income quintiles. https://marriagefoundation.org.uk/research/married-poor-more-stable-than-unmarried-rich/ Among the very poorest parents, 8.9 per cent of cohabiting couples separated each year against 2.8 per cent of married couples. The poorest married parents were slightly more stable than the richest cohabiting parents. https://marriagefoundation.org.uk/research/married-poor-more-stable-than-unmarried-rich/ The Centre for Social Justice's July 2026 report, The Stability Advantage, found the same. Over 14 years, and allowing for a wide range of social and economic differences, parents in the poorest fifth who married were less likely to separate, at 26 per cent, than parents in the richest fifth who never married, at 46 per cent. https://www.centreforsocialjustice.org.uk/newsroom/10000-couple-penalty-shatters-wedding-prospects-for-low-income-british-couples
Marriage is also the safer home. In the Crime Survey for England and Wales for the year to March 2025, 5.1 per cent of married or civil-partnered women had suffered domestic abuse in the previous year, against 10.2 per cent of cohabiting women and 14.1 per cent of single women. For men the figures were 3.7, 7.4 and 10.4 per cent. https://www.ons.gov.uk/peoplepopulationandcommunity/crimeandjustice/articles/domesticabusevictimcharacteristicsenglandandwales/yearendingmarch2025 https://www.ons.gov.uk/peoplepopulationandcommunity/crimeandjustice/datasets/domesticabuseprevalenceandvictimcharacteristicsappendixtables/yearendingmarch2025
The Marriage Foundation's 2025 report, We need to talk about marriage, records what the stability gap means for the country. https://marriagefoundation.org.uk/wp-content/uploads/2025/05/MF-note-We-need-to-talk-about-marriage.pdf Nearly half of teenagers, 43 per cent, aren't living with both natural parents, up from 9 per cent in 1974, and the Foundation's own estimate is 45 per cent. Married families are 85 per cent of intact parent couples, yet account for just 30 per cent of the breakdown. https://marriagefoundation.org.uk/wp-content/uploads/2025/05/MF-note-We-need-to-talk-about-marriage.pdf Family breakdown costs the state at least £64 billion a year, according to the Centre for Social Justice's estimate in its Lost Boys report of March 2025 - an earlier figure of £51 billion uprated for inflation. https://www.centreforsocialjustice.org.uk/wp-content/uploads/2025/03/CSJ-The_Lost_Boys.pdf
SLIDING VERSUS DECIDING
A related question is whether living together before marriage affects the marriage. The best evidence says the danger lies in moving in before deciding to marry. https://www.du.edu/news/new-du-study-highlights-risks-living-together-engagement
Galena Rhoades and Scott Stanley at the University of Denver surveyed a representative sample of around 1,600 Americans married for the first time between 2010 and 2019. https://www.du.edu/news/new-du-study-highlights-risks-living-together-engagement Among those who had moved in together before getting engaged, 34 per cent of the marriages had ended. Among those who waited until engagement or the wedding, it was 23 per cent. https://www.du.edu/news/new-du-study-highlights-risks-living-together-engagement Their earlier study of 1,050 recently married people, published in the Journal of Family Psychology in 2009, found the same pattern in satisfaction and confidence after controlling for education, length of marriage and religiousness. https://pmc.ncbi.nlm.nih.gov/articles/PMC5956907/
Their explanation has entered the language of the field as "sliding versus deciding". Couples drift into living together for convenience - the rent, the lease, not having to go home at the end of an evening - without ever making a decision about the future. Once in, the shared flat and the shared furniture create an inertia that can carry a couple into marriage by default. The effect is weaker or absent for couples who move in only after getting engaged, which points to the real variable - a clear decision to marry, made together before moving in. https://pmc.ncbi.nlm.nih.gov/articles/PMC5956907/ In Galena Rhoades's words, the risk lies in living together before a couple have made "a clear and mutual decision - and an announcement, even - to get married". https://www.du.edu/news/new-du-study-highlights-risks-living-together-engagement In the Denver survey, most of those who had lived together first described sliding into it rather than deciding. Nine in ten couples who marry now live together first - 89.1 per cent in 2023, according to the Office for National Statistics (ONS). https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/marriagecohabitationandcivilpartnerships/datasets/marriagesinenglandandwales2013 So what matters is whether a couple have decided to marry before they move in.
An analysis pooling 16 studies, published in 2010, found living together before marriage linked to a higher risk of divorce, but not when only living together with the eventual husband or wife was counted. Those couples, its authors suggest, "may attach more long-term meaning to living together". https://researchconnect.stonybrook.edu/en/publications/does-premarital-cohabitation-predict-subsequent-marital-stability/ In 2021 Wendy Manning, Pamela Smock and Arielle Kuperberg reported that living with a spouse before marriage was no longer linked to divorce among the most recent American marriages. https://doi.org/10.1111/jomf.12724 Michael Rosenfeld and Katharina Roesler replied that Manning and her co-authors had discarded more than 70 per cent of the valid data, and that "premarital cohabitation consistently predicts higher rates of marital dissolution in the U.S." https://onlinelibrary.wiley.com/doi/abs/10.1111/jomf.12744
WHAT IT MEANS FOR CHILDREN
Children need stability, and cohabiting unions are markedly less stable than marriages. The Institute for Fiscal Studies found in 2010 that 26 per cent of cohabiting couples had separated at least once by their child's third birthday against 7 per cent of married couples. By the fifth birthday, 27 per cent of the couples who had been cohabiting at the birth were no longer living together, against 9 per cent of the married. https://ifs.org.uk/sites/default/files/output_url_files/bn107.pdf The objection that stability, not marriage, is what matters runs into Wendy Manning's own review of cohabitation. Children born to cohabiting parents, she writes, see their parents break up more often, so that being born into a cohabiting family "sets the stage for later instability". https://pmc.ncbi.nlm.nih.gov/articles/PMC4768758/ Susan Brown's review of a decade's research found that children in two-biological-parent married families "appear to enjoy the best outcomes, on average", and that "stability alone is not sufficient to maximize children's outcomes". https://pmc.ncbi.nlm.nih.gov/articles/PMC3091824/
A second Institute for Fiscal Studies paper that year found that children born to cohabiting parents had more social and emotional difficulties at age three than children born to married parents. https://ifs.org.uk/sites/default/files/output_url_files/comm114.pdf Children whose cohabiting parents had split did worst. The gap narrowed but held as the parents' education, income and housing were allowed for, and closed only when their relationship quality was held constant. The authors warn that if marriage itself brings higher income, better relationships or better parenting, allowing for these "will lead to an understatement of the possible benefits of marriage". https://ifs.org.uk/sites/default/files/output_url_files/comm114.pdf A 2016 study for the Ministry of Justice by researchers at the London School of Economics found that "children of continuously married parents tended to have the best outcomes at age 11". https://dera.ioe.ac.uk/id/eprint/25543/1/child-outcomes-after-parental-separation.pdf
Studies that follow the same children through their parents' break-up show that the break-up itself does harm. Using American tax and Census records, Andrew Johnston, Maggie Jones and Nolan Pope followed 4.5 million children born between 1988 and 1993 to married parents who later divorced, and compared brothers and sisters who lived through the same divorce at different ages. Divorce early in childhood cut adult earnings by 9 to 13 per cent and raised the risk of a teenage birth by roughly 60 per cent, and of imprisonment and early death by about 40 and 45 per cent. https://www.nber.org/system/files/working_papers/w33776/w33776.pdf Comparing the same American children before and after their parents' divorce, Paul Amato and Christopher Anthony found the effects small, but judged the evidence that divorce caused them reasonably strong. https://pmc.ncbi.nlm.nih.gov/articles/PMC3956656/ In Norway's registers, children whose parents' marriage broke up were still 6 to 13 percentage points less likely to get through the main stages of secondary school, even after differences between their mothers that never show up in the records were allowed for. https://pmc.ncbi.nlm.nih.gov/articles/PMC2831341/ And following 6,245 Millennium Cohort children, Emla Fitzsimons and Aase Villadsen compared each child before and after a father left. A departure later in childhood raised emotional problems in boys and girls, and behaviour problems in boys. https://pubmed.ncbi.nlm.nih.gov/30660390/ Cohabiting parents split up far more often, so their children face more of that harm. The fuller evidence is on our page The Marriage Advantage. https://www.c4m.org.uk/marriage-support/the-marriage-advantage-why-children-thrive-with-married-biological-parents
The disadvantage runs into adulthood. The Marriage Foundation and Spencer James of Brigham Young University, analysing two British birth cohorts, found that people born to married parents were 23 per cent more likely to have gone to university, 16 per cent less likely ever to have drawn benefits as adults, and 10 per cent more likely to have married themselves - whatever their social background. https://ifstudies.org/blog/the-long-term-benefits-of-marriage-evidence-from-the-uk
The safest home for a child is with married biological parents. In the United States, the Fourth National Incidence Study of Child Abuse and Neglect found that children living with their two married biological parents had the lowest rate of maltreatment of any family arrangement. https://acf.gov/sites/default/files/documents/opre/nis4_report_congress_full_pdf_jan2010.pdf On the study's stricter measure, children whose single parent lived with an unmarried partner suffered abuse at more than 11 times the rate of children with married biological parents - 33.6 per 1,000 against 2.9. https://acf.gov/sites/default/files/documents/opre/nis4_report_congress_full_pdf_jan2010.pdf In Canada, Martin Daly and Margo Wilson found that pre-school children living with one natural parent and a stepparent were 40 times as likely to be recorded as child-abuse cases as children living with both natural parents. https://www.martindaly.ca/uploads/2/3/7/0/23707972/daly___wilson_1985_child_abuse.pdf Both are findings about unrelated adults in the home.
None of this shames the mother raising children alone, often heroically, or the couple who never married. The data describes risks across populations, not verdicts on people. But the structures aren't interchangeable, and a country that cares about children can't pretend they are.
SELECTION OR CAUSATION?
Would these couples have done just as well unmarried, because stable people are the ones who marry? The Institute for Fiscal Studies concluded in 2013 that the differences in relationship stability between married and cohabiting parents, and in their children's skills and behaviour, "mainly or entirely reflect the fact that different types of people choose to get married". https://ifs.org.uk/sites/default/files/output_url_files/r87.pdf Selection is real. The married are on average older, better educated and richer. But selection doesn't explain the whole gap. The 2013 report's own figures couldn't explain away the gap in teenagers' risky and antisocial behaviour. https://ifs.org.uk/sites/default/files/output_url_files/r87.pdf And the Institute's study of the parents, the Marriage Foundation points out, left out a quarter of the sample. The June 2026 re-analysis by the Marriage Foundation and the Centre for Social Justice put it back, and found that, comparing couples who married at any point with those who never did, 27 differences between them left between half and two thirds of the gap unexplained. https://marriagefoundation.org.uk/research/the-timing-of-marriage-and-union-dissolution/
The studies best able to tell cause from coincidence point the same way. Among 1,613 pairs of young American twins and siblings, Erin Horn and colleagues found that being married or living with a partner protected against depression, thoughts of suicide and drinking, and that marriage protected against crime in a way that living together didn't. https://pmc.ncbi.nlm.nih.gov/articles/PMC3645280/ Identical twins who were cohabiting were 67 per cent more likely than their married co-twins to have broken the law in the previous year. The link with physical health, they found, was completely explained by who marries. https://pmc.ncbi.nlm.nih.gov/articles/PMC3645280/ In Minnesota, among 289 pairs of male twins followed from 17 to 29, the married twin engaged in less antisocial behaviour after his wedding than his unmarried identical co-twin, even allowing for how he had behaved before. https://pubmed.ncbi.nlm.nih.gov/21135331/ When one study compared American twin brothers with each other, the wage premium of marriage didn't fall but rose, from 19 per cent when men were compared in the ordinary way to about 26 per cent between twins. Another twin study put it at 6 per cent, but with so large a margin of error that, as the first study's authors note, "it is difficult to infer much about the causal relationship". https://repository.upenn.edu/server/api/core/bitstreams/2cc7b4bf-4546-4f5f-950c-e92872b17898/content An American survey following the same people found that getting married significantly raised happiness within two years. https://ifstudies.org/blog/number-6-in-2022-does-getting-married-really-make-you-happier And a 2018 study in the European Economic Review found a health difference of around five percentage points at ages 55 to 59, even allowing for differences in people's underlying health that a survey would be unlikely to record. https://pmc.ncbi.nlm.nih.gov/articles/PMC7597938/
In the UK, the Marriage Foundation reports that "even after taking into account [mothers'] age, education, ethnicity, household income and relationship happiness, the odds of cohabiting parents splitting up are consistently twice as high as those of married parents". https://marriagefoundation.org.uk/research/married-poor-more-stable-than-unmarried-rich/ Its October 2026 study of 3,700 mothers in the Millennium Cohort Study looked at happiness as well. Among couples still together 14 years after their first child's birth, and allowing for each mother's age, education, income, psychological distress and how satisfied with life she had been soon after the birth, 59 per cent of mothers who married before the birth and 61 per cent of those who married afterwards were highly satisfied with life, against 49 per cent of those who never married. https://marriagefoundation.org.uk/wp-content/uploads/2026/10/MF-note-Married-Mums-are-Happiest-2026.pdf The fuller treatment is on our main evidence page, Why Marriage Matters. https://www.c4m.org.uk/marriage-support/why-marriage-matters The short answer is that both selection and cause are at work. More committed people marry, and marrying reinforces commitment. And how many people marry isn't fixed. It moves with the law, as Finland's experience shows.
EVEN WHERE LIVING TOGETHER IS THE NORM
The claim that the gap disappears where cohabitation is socially normal doesn't survive contact with the data. In Norway - where some scholars treat cohabitation as the functional equivalent of marriage - children born to cohabiting parents are about 88 per cent more likely to see their parents part than children born to married parents. Among college-educated Norwegian mothers, 17 per cent of children of cohabiting couples saw a split by age 12, against 8 per cent of children of married couples. https://www.brookings.edu/articles/in-europe-cohabitation-is-stable-right/ In France the gap is around 66 per cent, and visible among the highly educated. Across 16 countries surveyed in the late 1980s and 1990s, from Sweden to Italy and the United States, children born to cohabiting parents were more likely to see their parents part than children born to married parents in every one, and in practically every country about twice as likely. https://doi.org/10.4054/DemRes.2002.7.7 The size of the gap varies and the mechanisms are argued over, but the direction is the same everywhere it was measured.
Cohabiting parents don't behave like married ones even where living together is common. In a study of 15 countries, mothers who stayed cohabiting after a first birth had significantly lower odds than married mothers of conceiving a second child in 11 of them - between 29 and 55 per cent lower, after allowing for how long the union had lasted and whether it broke up. https://pmc.ncbi.nlm.nih.gov/articles/PMC4221046/ In the United Kingdom the odds were 45 per cent lower. Where couples married after the birth, the married pattern returned. Cohabitation, the author concludes, "should not be considered 'an alternative to marriage' or 'indistinguishable from marriage'". https://pmc.ncbi.nlm.nih.gov/articles/PMC4221046/ In the United States, among children born in the 2000s, 31.9 per cent of those born to cohabiting parents were living with their married biological parents at 14, against 74.9 per cent of those born to married parents. https://www.nber.org/system/files/working_papers/w35765/w35765.pdf
IF YOU'RE COHABITING NOW
Nobody should live without legal protection. Six steps close some of the gap:
The first and most important step is a will. Without one, your partner has no automatic right to inherit anything. https://www.gov.uk/inherits-someone-dies-without-will
Both names belong on the property, with a deliberate choice between joint tenancy (the survivor takes the whole) and tenancy in common (your share passes by your will).
We'd urge you to draw up a cohabitation agreement setting out what happens to property and money if you separate.
Pension nomination forms need filling in, so each scheme knows who your benefits are for.
A Lasting Power of Attorney lets your partner act for you if you lose capacity. Married couples need one too.
An unmarried father should be registered on the birth certificate jointly with the mother, or hold a formal agreement, so that he has parental responsibility.
These steps help, and every cohabiting family should take them, but they're workarounds. Marriage gives most of the other protections on this page automatically, by operation of law, the day you make the promise.
WHAT WE BELIEVE
Marriage is the voluntary, exclusive, lifelong union of one man and one woman, and the evidence on this page shows why it can't be replicated by paperwork. The public promise itself is what the protections and the stability grow from.
It's a scandal that nearly half the country still believes in a legal status that doesn't exist. https://news-archive.exeter.ac.uk/2019/january/title_700858_en.html Millions of families are banking on protections they don't have, and the Government, the legal profession and the media have a duty to say so clearly and repeatedly. The remedy is to tell people the truth, and to refuse a law that would turn cohabitation into marriage by another name.
The stability evidence is compelling. Cohabiting parents are more likely to separate than married parents in every income band and in every country of a 16-nation comparison. https://marriagefoundation.org.uk/research/married-poor-more-stable-than-unmarried-rich/ https://doi.org/10.4054/DemRes.2002.7.7 The children of those separations pay the longest price. Marriage is no guarantee, but it's the surest foundation a family can have. And the research on sliding versus deciding has a message for every couple considering the question. A shared address doesn't protect a family, but the deliberate, public, mutual promise does. Marriage is that promise in its fullest form, made before witnesses and backed by law.
In its consultation response, the Ministry of Justice must drop its plan to blur the line between marriage and cohabitation, and the state must back the institution the evidence backs - marriage. Every couple deserves to know the facts before they need them. The desire to marry is there. In a Survation survey of 1,011 teenagers for the Centre for Social Justice, published in February 2018, 78 per cent of 14 to 17-year-olds said they probably or definitely want to get married. https://www.survation.com/4-in-5-young-people-want-married-over-half-believe-forming-relationships-is-more-difficult/ Three quarters of Gen Z adults want to get married (75 per cent), according to an Opinium survey of 2,000 Gen Z adults aged 18 to 27 for Charles Russell Speechlys. https://www.charlesrussellspeechlys.com/en/insights/expert-insights/private-client/2025/gen-z-and-milestone-planning/ Yet on current trends only 58 per cent of Gen Z women and 56 per cent of Gen Z men in England and Wales will ever marry, according to Marriage Foundation analysis of ONS data in December 2024. https://marriagefoundation.org.uk/research/the-collapse-of-marriage-among-gen-z/ That's the gap we're working to close.
C4M runs marriage courses for churches and other organisations across the United Kingdom: Astonish the World for married couples and Building on Rock for couples preparing to marry. Details are at https://www.c4m.org.uk/marriage-support/marriage-courses. To find out more, or to book a course free of charge, email admin@c4m.org.uk.
Join us. Share this page with anyone living together, receive the Coalition for Marriage briefings at https://www.c4m.org.uk/subscribe, and support the campaign at https://www.c4m.org.uk/donate.
RELATED PAGES ON C4M.ORG.UK
Why Marriage Matters - https://www.c4m.org.uk/marriage-support/why-marriage-matters Marriage Facts and Figures - https://www.c4m.org.uk/marriage-support/marriage-facts-and-figures The Marriage Advantage: Why Children Thrive with Married Biological Parents - https://www.c4m.org.uk/marriage-support/the-marriage-advantage-why-children-thrive-with-married-biological-parents
KEY SOURCES
Every link on this page was accessed on 20 October 2026.
ONS, Families and households 2025. https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/families/bulletins/familiesandhouseholds/2025 ONS, Families and households 2025 workbook. https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/families/datasets/familiesandhouseholdsfamiliesandhouseholds ONS, Marriages 2023 workbook. https://www.ons.gov.uk/peoplepopulationandcommunity/birthsdeathsandmarriages/marriagecohabitationandcivilpartnerships/datasets/marriagesinenglandandwales2013 Centre for Social Justice, I Do? (2026). https://www.centreforsocialjustice.org.uk/wp-content/uploads/2026/02/CSJ-I_Do.pdf House of Commons Women and Equalities Committee, The rights of cohabiting partners (2022). https://committees.parliament.uk/publications/23321/documents/170094/default/ British Social Attitudes 2019 (Exeter). https://news-archive.exeter.ac.uk/2019/january/title_700858_en.html Ministry of Justice, A fairer end to relationships (2026). https://www.gov.uk/government/consultations/a-fairer-end-to-relationships Ministry of Justice, A fairer end to relationships, consultation document (2026). https://www.gov.uk/government/consultations/a-fairer-end-to-relationships/a-fairer-end-to-relationships-consultation-document Ministry of Justice, Impact assessment (2026). https://assets.publishing.service.gov.uk/media/6a1eee48050971fbebf3bd8b/Regulatory_Impact_Assessment_-_Cohabitation_and_Financial_Remedies_Reform_Consultation.pdf Ministry of Justice, The family test (2026). https://www.gov.uk/government/consultations/a-fairer-end-to-relationships/the-family-test-a-fairer-end-to-relationships HMRC, Pensions Tax Manual, PTM071200. https://www.gov.uk/hmrc-internal-manuals/pensions-tax-manual/ptm071200 Centre for Social Justice, Finnishing Marriage? (2026). https://www.centreforsocialjustice.org.uk/library/finnishing-marriage Marriage Foundation, Married poor more stable than unmarried rich (2022). https://marriagefoundation.org.uk/research/married-poor-more-stable-than-unmarried-rich/ Marriage Foundation, The Timing of Marriage and Union Dissolution (2026). https://marriagefoundation.org.uk/research/the-timing-of-marriage-and-union-dissolution/ Centre for Social Justice, The Stability Advantage (2026). https://www.centreforsocialjustice.org.uk/newsroom/10000-couple-penalty-shatters-wedding-prospects-for-low-income-british-couples ONS, Domestic abuse victim characteristics (2025). https://www.ons.gov.uk/peoplepopulationandcommunity/crimeandjustice/articles/domesticabusevictimcharacteristicsenglandandwales/yearendingmarch2025 Marriage Foundation, We need to talk about marriage (2025). https://marriagefoundation.org.uk/wp-content/uploads/2025/05/MF-note-We-need-to-talk-about-marriage.pdf Rhoades, Stanley and Markman, Journal of Family Psychology (2009). https://pmc.ncbi.nlm.nih.gov/articles/PMC5956907/ Institute for Fiscal Studies, Briefing Note BN107 (2010). https://ifs.org.uk/sites/default/files/output_url_files/bn107.pdf Institute for Fiscal Studies, Commentary C114 (2010). https://ifs.org.uk/sites/default/files/output_url_files/comm114.pdf Institute for Fiscal Studies, Cohabitation, marriage, relationship stability and child outcomes, final report (2013). https://ifs.org.uk/sites/default/files/output_url_files/r87.pdf Johnston, Jones and Pope, NBER Working Paper 33776 (2025). https://www.nber.org/system/files/working_papers/w33776/w33776.pdf Horn and colleagues, Journal of Family Psychology 27(1) (2013). https://pmc.ncbi.nlm.nih.gov/articles/PMC3645280/ Perelli-Harris, European Journal of Population (2014). https://pmc.ncbi.nlm.nih.gov/articles/PMC4221046/ Kearney, Levine and Barson, NBER Working Paper 35765 (2026). https://www.nber.org/system/files/working_papers/w35765/w35765.pdf National Incidence Study, Report to Congress (2010). https://acf.gov/sites/default/files/documents/opre/nis4_report_congress_full_pdf_jan2010.pdf Marriage Foundation, Married Mums Are the Happiest (2026). https://marriagefoundation.org.uk/wp-content/uploads/2026/10/MF-note-Married-Mums-are-Happiest-2026.pdf Manning, Cohabitation and Child Wellbeing, The Future of Children (2015). https://pmc.ncbi.nlm.nih.gov/articles/PMC4768758/ Jose, O'Leary and Moyer, Journal of Marriage and Family (2010). https://researchconnect.stonybrook.edu/en/publications/does-premarital-cohabitation-predict-subsequent-marital-stability/ Andersson, Demographic Research 7(7) (2002). https://doi.org/10.4054/DemRes.2002.7.7
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