April 16, 2026 | News | New Publication

People With a Similar Risk of Divorce are More Likely to Marry Each Other

A recent study shows that: Spouses are very similar in terms of their risk of separating

A study by the Max Planck Institute for Demographic Research (MPIDR) and the Norwegian Institute of Public Health found that spouses tend to be very similar in terms of their risk of separation. Marriage is shaped not only by a person's own background, but also by that of their partner. The analysis of over 350,000 Norwegian marriages reveals a previously underestimated phenomenon: people with a similar risk of divorce tend to marry one another.

A recent study by the Max Planck Institute for Demographic Research (MPIDR) and the Norwegian Institute of Public Health examined how a couple’s in-laws relate to their risk of divorce. © istockphoto.com / Deagreez

This study, published in the journal Twin Research and Human Genetics, is the first to systematically investigate whether divorce patterns also recur among 'in-laws. The researchers used data from nationwide register analyses covering more than 100,000 extended families and tracked not only biological kinship, but also the marriages of siblings and in-laws.

'A couple’s risk of divorce is higher if the husband’s brother’s wife’s sister’s husband’s brother’s marriage has also ended in divorce,' explains Philipp Dierker, a researcher at the MPIDR. Put simply, this means: Paul and Anna are a married couple. Paul’s brother Hank is married to Sarah. Their sister Hanna, in turn, is married to Dennis. Dennis has a brother, Robert – and if Robert’s marriage ends in divorce, the risk of divorce for Paul and Anna also increases. 'This is no coincidence. It suggests that people with similar risk profiles for divorce find each other.'

© MPIDR

The similarity between spouses in terms of divorce risk is so strong that it cannot be explained by shared childhood experiences, genetic kinship, or social environment alone. Instead, the research suggests that people with similar family risk factors, such as coming from a family with frequent separations, are drawn to one another, either consciously or unconsciously.

The researchers estimate that the divorce rate in Norway would be around 8 per cent lower if spouses did not match so closely in their risk profiles. ‘Much of what we interpret as individual risk is actually influenced by the choice of partner,’ explains Hans Fredrik Sunde of the Norwegian Institute of Public Health. At the same time, the researchers emphasize that reality is more complex than such a hypothetical scenario.

Divorce is usually studied as an individual outcome. But nobody gets divorced on their own. 'Traditional approaches that view divorce as a purely individual phenomenon overlook the fact that the choice of partner has a decisive influence on the outcome of the marriage,' says Sunde. ‘If we want to understand why marriages fail, we must look at the relationship between the partners as a whole, not just at the individuals.’

It is also notable that family factors on the wife’s side are a stronger predictor of divorce than those on the husband’s side. This is consistent with the fact that women in Norway file for divorce significantly more often. Most striking, however, was the strong correlation between risk factors among spouses; their family backgrounds were closely intertwined.

The study is part of a larger research program aimed at systematically investigating couple phenomena. ‘When something happens between two people — be it marriage, pregnancy, or a shared illness — we must analyze it as a couple phenomenon,’ emphasizes Dierker. 'Otherwise, we run the risk of misinterpreting the causes. The reality is more complex than we previously thought.'

The developed method can also be used to investigate other shared life events in future, such as fertility, health behavior and social integration. “In future, research should focus on analyzing couples, not just individuals,” says Dierker.

Original Publication

Sunde, H.F., P. Dierker (2026): "Are Spouses Similar in Divorce? Investigating Spousal Similarity in Couple-Shared Outcomes." Twin Research and Human Genetics. DOI: 10.1017/thg.2026.10050

Keywords

Union dissolution | Divorce | Twins | Affines | Assortative mating