Sibling bullying is one of the most common forms of family aggression, yet it remains widely dismissed as normal rivalry, even when its effects persist well into adulthood. Roughly half of emerging adults in a large cross-country study reported having experienced sibling bullying during their upbringing, and the mental health consequences can be as serious as those linked to peer bullying or parental abuse. The problem is compounded by the fact that many adults carry these wounds silently, having internalized the message that what happened between siblings “doesn’t count.”
How Common Sibling Bullying Actually Is
Most people assume bullying is something that happens at school. The reality is that for many children, the most frequent aggressor lives under the same roof. A 2024 cross-country investigation of over 3,400 emerging adults found that approximately 50 percent reported experience with sibling bullying, making it far more widespread than many families acknowledge.1PubMed. Sibling bullying reported by emerging adults: Profiling the prevalence, roles, and forms in a cross-country investigation That figure covers people looking back at their childhood and adolescent years, but the patterns it describes don’t simply vanish when siblings turn eighteen. For some, the dynamic continues in modified forms through adulthood: verbal put-downs at family gatherings, exclusion from decision-making, manipulation around shared responsibilities like eldercare, or ongoing psychological control.
One reason sibling bullying stays invisible is that families and professionals alike tend to frame it as rivalry. The distinction matters. Rivalry implies a roughly equal contest over resources or parental attention. Bullying involves a power imbalance and repeated aggression, whether physical, verbal, or relational. When researchers use the term “sibling bullying,” they mean something closer to the latter, and the outcomes reflect that severity.
The Forms It Takes
Verbal aggression is the most frequently reported type of sibling bullying across both sexes, well ahead of physical, relational, or technological forms.2PubMed. Sibling bullying reported by emerging adults: Profiling the prevalence, roles, and forms in a cross-country investigation That means name-calling, belittling, threats, and chronic criticism dominate the landscape. Physical aggression, while it gets more attention because it’s visible, occurs less often. Relational bullying, which includes spreading rumors, turning family members against the target, or using social exclusion as a weapon, rounds out the picture. Technological bullying through text messages and social media exists but is reported least frequently.
The roles people play are also worth understanding. The most commonly reported role in that cross-country study was the bully-victim, someone who both perpetrates and is targeted. This held true for both males and females. When the dual role wasn’t present, males were more likely to be the bully and females more likely to be the victim as a secondary pattern. This is different from how peer bullying tends to sort itself, and researchers have noted that sibling bullying operates by its own rules: the constant proximity, the inability to escape, and the emotional complexity of a family bond all make it a distinct phenomenon.
The Mental Health Toll in Adulthood
The idea that childhood sibling bullying is something people “grow out of” doesn’t hold up against the evidence. A large prospective study using data from over 6,900 individuals in the UK found that sibling bullying at age twelve predicted serious outcomes years later. Frequent victims had nearly triple the odds of nicotine dependence by their late teens and early twenties, and frequent perpetrators had elevated odds of antisocial behavior.3Aggressive Behavior. Sibling bullying at 12 years and high‐risk behavior in early adulthood: A prospective cohort study These associations held even after the researchers accounted for peer bullying and parental maltreatment, meaning the sibling relationship had an independent effect.
The psychological scars go deeper than risk behaviors. A separate study examining clinical outcomes in early adulthood found that people who had been sibling bully-victims were roughly twice as likely to meet diagnostic criteria for depression. Those who had been victims specifically showed increased odds of suicidal ideation and more than double the odds of suicidal self-harm, again independent of peer bullying and a range of childhood risk factors.4PubMed Central. The Independent and Cumulative Effects of Sibling and Peer Bullying in Childhood on Depression, Anxiety, Suicidal Ideation, and Self-Harm in Adulthood That last point deserves emphasis. Even when children were also bullied at school, the additional effect of being bullied at home by a sibling made things measurably worse.
Beyond clinical diagnoses, adults who experienced sibling bullying report lower self-esteem, a weaker sense of personal competence, reduced life satisfaction, and more internalized problems like chronic anxiety and self-blame.5Journal of Interpersonal Violence. Family Dynamics and Young Adults’ Well-Being: The Mediating Role of Sibling Bullying These aren’t dramatic crisis-level symptoms that force people into emergency rooms. They’re the quieter kind of suffering: a persistent feeling of inadequacy, difficulty trusting your own judgment, a sense that you’re somehow less capable than those around you. Because these effects develop gradually and are so closely tied to a person’s earliest social environment, they can feel like personality traits rather than consequences of what happened at home.
How Parents Shape the Dynamic
Sibling bullying doesn’t emerge in a vacuum. The family environment in which it develops plays a substantial role, and parental behavior is a major driver. Young adults who recalled higher levels of sibling rivalry and hostility between their parents were significantly more likely to report having been victims of sibling bullying.6Journal of Interpersonal Violence. Family Dynamics and Young Adults’ Well-Being: The Mediating Role of Sibling Bullying Interparental conflict models aggression as a way to resolve disagreements, and children absorb those lessons faster than most parents realize.
Favoritism is another powerful ingredient. Research on adult siblings has found that memories of maternal favoritism during childhood were more important than perceptions of current favoritism in predicting tension between siblings, regardless of how old the siblings were at the time of the study.7PubMed Central. The Role of Perceived Maternal Favoritism in Sibling Relations in Midlife In other words, the damage from a parent visibly preferring one child over another can echo through decades. The favored child may develop an inflated sense of entitlement within the sibling hierarchy, while the disfavored child may internalize resentment or a sense of worthlessness, both of which feed bullying dynamics.
Paternal favoritism operates somewhat differently. A study of adult children found that when they perceived their father as currently favoring one sibling, it predicted tension, whereas current maternal favoritism did not have the same effect. The father’s favoritism was a stronger predictor of tension for daughters than for sons.8The Journals of Gerontology Series B Psychological Sciences and Social Sciences. Differential Effects of Perceptions of Mothers’ and Fathers’ Favoritism on Sibling Tension in Adulthood This suggests that sibling conflict isn’t driven by one uniform parental force. Mothers’ past behavior and fathers’ present behavior each leave their own mark, and those marks can persist long after the siblings have left home.
What It Does to Personality and Later Relationships
The effects of sibling bullying aren’t confined to how you feel about yourself. They can shape the kind of person you become and how you relate to others. A study of adults found that the amount of conflict people recalled having with siblings during adolescence was positively correlated with traits like Machiavellianism and psychopathy, two personality patterns characterized by manipulation, emotional detachment, and disregard for others.9Current Psychology. Sibling relationship quality and parental rearing style influence the development of Dark Triad traits On the flip side, feeling close to siblings was negatively associated with Machiavellianism. And when parents were perceived as partial toward the other sibling, narcissism scores tended to be higher. These correlations don’t prove that sibling conflict causes these traits outright, but they strongly suggest the sibling relationship is an underappreciated training ground for how people learn to interact with the world.
Romantic relationships also appear to absorb the fallout. A study of Italian university students in their twenties found that more positive attitudes toward sibling relationships predicted higher romantic relationship quality, while avoidant attachment patterns pulled that quality down.10Journal of Family Issues. Predicting Young Adults’ Romantic Relationship Quality: Sibling Ties and Adult Attachment Styles If your formative experience of close family relationships involved hostility, manipulation, or chronic insecurity, it makes sense that you’d bring those expectations into your adult partnerships. You might struggle with trust, withdraw from conflict rather than engaging constructively, or tolerate mistreatment because it feels familiar.
When It Leads to Estrangement
For some adults, the eventual response to a bullying sibling isn’t therapy or reconciliation but cutting off contact entirely. A qualitative study of estranged adults in the United States identified two interlocking pathways to sibling estrangement. One ran through the family system: parental partisanship, favoritism, manipulation, or the sibling tie becoming collateral damage when the person cut off a parent. The other ran through the sibling’s own behavior: a meaningful childhood bond that never formed in the first place, destabilizing conduct such as substance use or erratic behavior, or a deliberate decision to contain risk when the sibling was perceived as a direct threat to safety.11Journal of Marriage and Family. Pathways to Adult Sibling Estrangement: Perspectives of Estranged U.S. Adults
Most people in that study described both pathways operating simultaneously, a pattern the researchers called “layered estrangement.” It was rarely just one dramatic event. Instead, years of accumulated grievances across multiple domains, family-level dysfunction on top of individual sibling aggression, eventually crossed a threshold. The decision to go no-contact often came after repeated attempts to set boundaries or change the dynamic had failed.
This is worth understanding because estrangement from a sibling still carries social stigma. People who cut off a brother or sister are frequently told they’re overreacting or that “family is family.” The research paints a more sympathetic picture: estrangement often represents a rational response to a genuinely harmful situation, not an impulsive decision made in anger. For adults who grew up being bullied by a sibling and found that the dynamic never really changed, distance may be the most protective option available.
Why It Stays Hidden
One of the most frustrating aspects of adult sibling bullying is how effectively it hides in plain sight. Several forces conspire to keep it unrecognized. Parents who witnessed or even facilitated the dynamic in childhood are unlikely to name it as bullying, because doing so would implicate their own parenting. The siblings themselves may have normalized it so thoroughly that they don’t have language for what happened. And the broader culture has a deeply ingrained narrative about sibling relationships being fundamentally benign, a story about teasing, roughhousing, and competition that is supposed to build character.
Researchers have pointed out that sibling bullying has received far less scholarly attention than peer bullying or other forms of family violence like intimate partner abuse or child maltreatment, despite being at least as prevalent as some of those categories.12Journal of Interpersonal Violence. Family Dynamics and Young Adults’ Well-Being: The Mediating Role of Sibling Bullying This academic neglect mirrors the cultural one. When something isn’t studied, it doesn’t make it into clinical training, which means therapists may not ask about it and clients may not volunteer it. The result is a self-reinforcing cycle of invisibility.
Adults who recognize their experience as sibling bullying often describe a delayed revelation, a moment in their twenties or thirties when a conversation, a book, or a therapy session reframes what they always thought was normal. That delay itself has consequences. Years of attributing their anxiety or self-doubt to personal failings rather than to a recognizable pattern of family aggression can compound the original harm.
Getting Help and What to Look For in Therapy
If you recognize yourself in any of this, the first thing to understand is that recovery from sibling bullying in adulthood is often slow and nonlinear. Qualitative research on survivors of sibling abuse has found that many people struggle to disclose what happened, even in a therapeutic setting, partly because the abuse is embedded within complex family relationships that the person may still be navigating.13Child Abuse & Neglect. “Just listen to me”: Experiences of therapy after childhood sibling sexual abuse Therapists who work effectively with this population tend to prioritize creating trust and validating the client’s narrative before pushing toward specific therapeutic techniques. Different modalities may be helpful at different stages, meaning there’s no single treatment approach that works for everyone at every point in recovery.
When looking for professional support, it helps to find someone who understands family systems and doesn’t default to reconciliation as the goal. Not every sibling relationship can or should be repaired. A therapist who pushes reunion without first understanding the power dynamics risks replicating the original invalidation. The work often involves untangling the internalized messages from childhood: that you deserved it, that it wasn’t that bad, that you should have fought back, that being upset about a sibling makes you weak. These beliefs can be remarkably durable, and dislodging them takes time and patience from both the client and the clinician.
For adults whose sibling bullying has evolved into an ongoing adult dynamic, boundary-setting becomes a central therapeutic task. This might mean reducing contact, changing the terms of engagement at family events, or learning to recognize and disengage from manipulative communication patterns. For those who have already chosen estrangement, the therapeutic focus often shifts toward grief, processing the loss of a relationship that was supposed to be lifelong, and building an identity that doesn’t hinge on the family role you were assigned as a child.
The Bully-Victim Overlap
One complication that makes sibling bullying harder to talk about than peer bullying is the high rate of the bully-victim role. In the cross-country prevalence study, being both a bully and a victim was the single most common experience reported, more common than being purely a bully or purely a victim.14PubMed. Sibling bullying reported by emerging adults: Profiling the prevalence, roles, and forms in a cross-country investigation This blurriness creates real problems for how people process their histories. If you hit your brother and your brother hit you, does that mean you were both at fault? Does that cancel out the harm?
The research suggests it doesn’t. Bully-victims had distinct and serious outcomes: they were specifically at elevated risk for depression in adulthood, and the prospective UK cohort study flagged them alongside pure bullies as being at particular risk for high-risk behavior.15PubMed Central. The Independent and Cumulative Effects of Sibling and Peer Bullying in Childhood on Depression, Anxiety, Suicidal Ideation, and Self-Harm in Adulthood16Aggressive Behavior. Sibling bullying at 12 years and high‐risk behavior in early adulthood: A prospective cohort study The fact that you also acted aggressively doesn’t erase the psychological impact of being victimized. Children who are bullied by a sibling and retaliate aren’t engaging in a fair contest; they’re often responding to an ongoing power imbalance with the only tools available to them. Adults who dismiss their own suffering because they “gave as good as they got” may be missing the full picture of what the dynamic cost them.