Which sibling pairs are closer, brothers or sisters? Research answers the age-old debate.

The sibling dynamic brings out the best in some people. At least in theory, if two people share blood, shouldn’t that result in a feeling of closeness? Growing up, I always envied my peers who had legitimate friendships within their families. In contrast, I fought constantly with my immediate older brother—we’ve only settled into a healthier, more comfortable relationship as adults, with teenage angst in the rear view.

But everyone’s situation is different. Some people lose touch with siblings as time flows on, pulled apart by life's responsibilities. For others, the maturity of adulthood heals once-festering wounds. Sibling dynamics ebb and flow like any friendship, but is there a discernible difference between brother and sister pairs throughout life? If you consult the research, you’ll find some interesting trends.

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Brother or sister bonds?

For a 2020 study published in the Journal of Family Psychology, researchers aimed to explore sibling bonds in later adulthood, assessing possible links between these relationships and loneliness or well-being. Analyzing 329 men and 279 women, averaging 64.6 years old, they found that older adults "reported high levels of sibling warmth" overall, along with "low levels of sibling conflict and parental favoritism." More specifically, they found that "sister-sister pairs had warmer sibling relationships than other gender compositions."

In 2025, Psychology Today reviewed similar research in an article focused on the "lifelong benefits" of close sibling bonds. They also reported differences by gender, noting that "compared to men, women tend to report receiving more support of any kind from siblings," and that this support is more common among those who identify as the same gender. "Sister-sister pairs," they wrote, "report receiving the most support from a sibling compared to brother-brother or mixed-gender pairs."

Sibling-relationship quality may also depend on the type of contact one has. Researchers at Brigham Young University broke down data into four patterns of contact ("low, medium, high, and traditional"), finding that those with "high contact reported greater life satisfaction than those in the other groups." Overall, these findings suggested that some forms of contact could "promote well-being." In contrast, others could offer reminders of "hurtful or painful past family experiences related to mothers’ differential treatment, in which case more contact may be linked to poorer health."

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Every sibling relationship is unique.

There are so many factors to consider here—as Psychology Today notes, "...There’s no such thing as a one-size-fits-all sibling relationship." They highlight a "solid body of research" showing that people who identify as "lesbian, gay, or bisexual tend to have less contact with their siblings than their heterosexual counterparts," adding that socioeconomic differences between siblings can also add strain.

If you burrow down into this rabbit hole of a topic, you’ll naturally find some side paths to explore. We recently reported on a 2025 Oxford Academic study that examined differences in aggression between women and men, including siblings, across cultures. Co-author Douglas Kenrick told PsyPost, "All the earlier research suggested two truisms about aggression: 1. Males are more aggressive, and 2. People are kinder to their blood relatives. Yet, we found that when it comes to hitting or yelling at another person, a) people are more likely to aggress towards brothers and sisters than toward friends or acquaintances, and b) sisters are at least as aggressive as brothers."

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