RESEARCH_FILE
The Science of Adult Sibling Dynamics
Most families never vote on who's the favorite, the screwup, or the reliable one — the roles just harden, usually before anyone in them could argue back.
SEE THE PRACTICE
Turn a thought this research explains into one clear move.
THE THOUGHT
“My parents always choose my sibling”
YOUR RECORDED RESPONSE
“Their preference for my sibling is a fact about their choices, not a verdict on my value.”
ONE PRIVATE MOVE
For three days, when you notice yourself interpreting a family moment, write down only what happened—the fact, not the meaning. At the end, read what you've written. Notice what's real and what's story.
Decades of research on parental treatment and adult sibling relationships show what that leaves behind: measurable differences in how parents treat their children, adult siblings who can describe the gap in specific detail, and a self-story — 'less loved,' 'the problem,' 'the fixer' — that keeps running whether or not anyone still believes it. Here's what the data says about who gets cast into which role, why it doesn't dissolve just because you've changed, and why more than one in four adults ends up estranged from a sibling at some point — usually for reasons bigger than either sibling alone.
How the science changed
- 1960
Vogel and Bell describe the 'family scapegoat': a child who absorbs and embodies unresolved conflict between other family members, becoming the visible symptom of a problem that isn't really theirs. ↗
- 1995
Victor Cicirelli's Sibling Relationships Across the Life Span consolidates decades of research showing that sibling bonds keep changing well into old age — the closeness, rivalry, and roles set in childhood are not a fixed sentence, even though they often feel like one. ↗
- 2013
Jensen and colleagues run the first study to directly measure differential treatment between adult siblings, rather than recall it from childhood: the sibling who reports getting less parental support than their brother or sister shows significantly more depressive symptoms. ↗
- 2013
Gilligan, Suitor and colleagues find that perceived paternal favoritism — not maternal — predicts tension between adult siblings, and the effect lands hardest on daughters who see their father favoring someone else. ↗
- 2015
Suitor and colleagues find that feeling like the favorite and feeling like the least-favored both predict more depressive symptoms in midlife adult children — being singled out carries a cost in either direction. ↗
- 2018
Peng, Suitor and Gilligan show that adult children's recollections of childhood favoritism predict their depressive symptoms decades later, regardless of birth order, gender, or what the relationship with the parent looks like today. ↗
- 2023
Hank and Steinbach's panel study of nearly 6,000 adults finds that 28% have gone through at least one period of estrangement from a sibling — usually triggered by disruptive family events like parental divorce or death, not simply a personality clash. ↗
What people believe vs. what the data shows
The belief“If your parents don't play favorites anymore, whatever it did to you and your sibling is over.”
The dataRecalled childhood favoritism keeps predicting adult children's depressive symptoms years later, independent of birth order, gender, or the current relationship with the parent — the old treatment leaves a mark that doesn't erase just because the treatment stopped. ↗
The belief“Parents don't actually play favorites — kids just imagine it because they're sensitive.”
The dataDifferential treatment is measurable, and adult children detect it accurately enough that it independently predicts depression and sibling tension — perceived paternal favoritism in particular reliably tracks with more conflict between siblings. ↗
The belief“There's no downside to being the golden child — favoritism only helps the one on the receiving end.”
The dataFeeling singled out as the favorite predicts higher depressive symptoms too, not just feeling passed over — being anyone's point of comparison carries a psychological cost, not only landing on the losing end of it. ↗
The belief“Sibling estrangement means something is uniquely broken in your family.”
The dataAbout 28% of adults have gone through a period of estrangement from a sibling, and it's most often tied to structural family disruptions like parental divorce or death — not a moral failure unique to one family. ↗
The belief“The role you got stuck with as a kid — the difficult one, the reliable one — describes who you actually are.”
The dataThe family-scapegoat concept describes how a role can be assigned to one person to absorb tension that actually belongs to the whole family system — the label was never a diagnosis of that person's character. ↗
TEST_YOURSELF · How well do you know this science?
01 Where does the 'family scapegoat' concept in family-systems research come from?
Vogel and Bell's 1960 paper described how an emotionally disturbed child could embody and carry unresolved tension between other family members — the origin of what's now called the family scapegoat role. source ↗
02 In Jensen and colleagues' 2013 study, what did siblings who received less parental support than their brother or sister report?
Jensen and colleagues found that among 151 sibling pairs, the offspring who reported receiving less parental support relative to their sibling reported significantly more depressive symptoms. source ↗
03 Gilligan and colleagues (2013) found that perceived favoritism by which parent predicted more sibling tension in adulthood?
Gilligan, Suitor, Kim and Pillemer found that perceived paternal favoritism predicted sibling tension in adulthood, while perceived maternal favoritism did not — and the effect was strongest for daughters. source ↗
04 According to Peng, Suitor and Gilligan (2018), recalling childhood favoritism predicted adult depressive symptoms:
Peng, Suitor and Gilligan found that both childhood recollections and current perceptions of maternal favoritism predicted depressive symptoms, with no moderating effect of birth order or gender — the link held across family positions. source ↗
05 Hank and Steinbach's (2023) large panel study found that sibling estrangement is most often triggered by:
Using pairfam panel data on 5,729 people, Hank and Steinbach found sibling estrangement was best predicted by structural characteristics of the sibling relationship and disruptive family events — especially parental divorce or death — rather than one-off conflicts. source ↗