How Divorce May Spread Between Siblings

Those of us who grew up as an older sibling probably recall our parents reminding us on numerous occasions to “Watch what you do because your little sister (or brother) looks up to you!” Whether we wanted the job or not, we were expected to be role models, and for many of us, that responsibility followed us into adulthood.

A new study from the Netherlands provides another reason to “watch what we do” when it comes to our marriages: divorce may spread between siblings.

The infectious nature of divorce between generations is well established: adults with divorced parents have a significantly higher risk of divorcing themselves—a risk that increases with each parental relationship transition they experienced as a child. As Nicholas Wolfinger explained on this blog about the intergenerational effects of divorce, “The established insight is that every family structure transition a child experiences in his or her family of origin cumulatively increases the likelihood of negative outcomes for that child.”

There is also evidence that divorce may spread among friends. Luma Simms recently reflected on the “infectious” nature of divorce, with one U.S. study finding that “The contagion of divorce can spread through a social network like a rumor, affecting friends up to two degrees removed.”

A new study published in Archives of Life Course Research (in press) builds on this research to show that the divorce of one sibling can increase the divorce risk of another sibling—with the effects as strong as having a divorced parent. The study by Elise de Vuijst, Anne-Rigt Poortman, Marjolijn Das, and Ruben van Gaalen found that even after controlling for a number of factors, “having a divorced sibling is associated with an increased likelihood of having a divorce oneself.”

The authors used nationwide registry data in the Netherlands and selected individuals ages 30 and up from five different birth cohorts, limiting their sample to married individuals with one full married sibling. They focused only on those in heterosexual marriages and did not include cohabiting couples. They then followed the married adults (total: 64,677) and their married siblings from 2000 to 2012.

According to the authors, the study is only the second to examine the cross-sibling effects on divorce and the first to consider if specific relationship characteristics between siblings might impact the divorce risk, especially characteristics related to role modeling. Their main theory is that “there is a direct association between siblings’ decisions on divorce because of the role model relationship siblings have.”

They acknowledge that establishing this connection is difficult since siblings share genes, family characteristics (like parental divorce), and income—all of which can impact the risk of divorce. So they controlled for a long list of demographic variables associated with an increased risk of divorce, including age at first marriage, education, income, and more. Additionally, they controlled for shared family background characteristics also known to increase the risk of divorce, such as the divorce of one’s parents. To address the possibility of genetic influence, they included a small sample of same-sex and opposite-sex twins. And they looked at whether the cross-sibling divorce effects changed over time.

The study considered whether certain “sibship” characteristics increase or decrease the effects of divorce between siblings, including: 1) level of contact (measured by geographical distance between siblings); 2) similarities, such as education, income level, and employment status; 3) gender (or whether same-sex siblings might have more influence than opposite-sex siblings); and 4) age (or that the divorce of older siblings would have a stronger effect than the divorce of younger siblings).

Overall, there was a 21% increased risk of divorce for individuals with a divorced sibling compared to individuals in the study with a married sibling. After introducing the controls, the cross-sibling effects on divorce decreased but remained "highly significant."

The study did not find evidence to support the theory that geographical distance, similarities, or gender moderate the effects on divorce. In their twin study, they found no evidence of genetic effects but note that their sample “was too small to draw any definitive conclusions.”

However, they did find support for their theory that the cross-sibling effects on divorce are linked to role modeling. That’s because an older sibling's divorce had a stronger effect than a younger sibling’s divorce. Moreover, the effects of a sibling's divorce significantly weakened over time. The authors explain:

As genetic or other family background influences on divorce would be static over time, these results strengthen our core expectation of a causal association between sibling’s divorce risks, not merely due to shared background and family characteristics, but additionally due to effects arising from a sibling role model mechanism.

Importantly, other background characteristics, from education level to the presence of children in the home, had a larger effect on divorce risk than a sibling’s divorce. Even so, the authors note, the “sibling effect is not negligible or even small: it is just as strong as the effect of parental divorce.”

While they underscore that their results do not explain “the causal influence” of the sibling effects on divorce, the authors speculate that sibling role modeling plays a major role:

The transmission of divorce behavior between siblings could be due to behavioral imitation, or perhaps a change in one’s norms on divorce when witnessing it in a close peer. Also, the divorce of a sibling could raise questions on one’s own relationship quality or send a ripple through the family when spouses ‘take sides’.

Whether the cross-sibling effects on divorce are due to family background or sibling role modeling, or a little of both, the study’s findings are a reminder of the power of individual marriages to negatively or positively influence the marriages around them. Marriage is indeed a "community affair," impacting not only the married couple and their children, but also their extended family, friends, and neighbors. Whether we realize it or not, other couples, especially those within our own families, are watching what we do, so let's strive to model marriages that last.

​​​​​​Alysse ElHage is editor of the Institute for Family Studies blog.

Editor’s Note: The views and opinions expressed in this article are those of the author and do not necessarily reflect the official policy or views of the Institute for Family Studies.