The Long-Term Impact of Sibling Aggression on Adults

This post was co-written with Amy Meyers, Ph.D., LCSW, a professor at Molloy University, psychotherapist, and expert on sibling abuse.

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Siblings play an important and enduring role in many people’s lives, even into adulthood. Brothers and sisters can be valuable sources of support and companionship, but what about those whose sibling relationships are more fraught? Sibling relationships shape our sense of friendship, loyalty, perspectives on trust, and perceptions of self. When there is a positive sibling relationship, there is a greater tendency towards healthy peer and adult relationships. But being hurt or mistreated by a sibling in childhood can have long-term consequences on well-being and the quality of adult relationships.

Sibling Victimization in Childhood

It is difficult to think about one child harming another, particularly within the same family, but sibling victimization is a common occurrence in childhood, with nearly half of U.S. children victimized by a brother or sister. Sibling victimization encompasses mistreatment by a brother or sister through physical assault, such as hitting, punching, or kicking with or without injury, or psychological aggression, like making threats of harm and constant belittling. Although pervasive, these kinds of sibling behaviors are generally unrecognized as concerning. Instead, aggressive, and even abusive, behaviors between siblings are typically equated to sibling rivalry and viewed as harmless normative behavior.

Impact on Adults’ Well-Being and Relationships with Others

In adulthood, sibling relationships are less intense, and the relationship becomes more voluntary than in childhood. Yet, talk to adults about their siblings, and you may notice that decades-old grievances and injuries remain salient.

Although no national-level data exists on how often sibling victimization occurs in adulthood, a consistent body of research shows that being victimized by a sibling in childhood is associated with mental health difficulties across the lifespan, including depression, anxiety, and suicidal ideation. Sibling victimization has also been linked to intimate partner violence and peer bullying. Far from being harmless and benign, childhood sibling victimization can enduringly affect the way people feel about themselves and relate to others.

Adults victimized by a sibling in childhood may still be experiencing aggression or abuse from that sibling, or they may have decided to limit or end contact (emotionally or physically cut off). In either case, having an aggressive or distant sibling relationship in adulthood may result in feeling powerless and hopeless and engaging in self-blame. Incidents of sibling victimization also can impact relationships with other siblings and parents, creating divided loyalties within the family. This can be especially relevant when adult siblings confront end-of-life issues for their parents.

The harm adults experience from their siblings, either in childhood or continued into adulthood, is related to having trouble trusting and becoming close with others. When a sibling violates and betrays the trust that comes with an implicit or assumed sibling bond, the harmed sibling may defend against further hurt through a myriad of relational patterns that limit intimate relatedness. To avoid anger directed at them, adults may display a strong need to please and adapt to the needs of others. Or they may be steadfastly self-reliant because depending on others may result in further perceived hurt.

Recommendations for Professionals Working With Adults

The potential impacts of childhood sibling victimization on adults’ well-being have important implications for practitioners and clinicians. Clinicians often rely on the exploration of historical and current parental impact on functioning. Clinical, human service, and medical personnel should assess the nature and quality of sibling interactions, as they underpin various presenting problems, including familial and interpersonal relationship issues and violence. Due to the lack of societal validation of this phenomenon, most clients will not have considered the impact of their sibling relationship and will not initiate offering this information.

Recognizing and responding to sibling victimization is critical given its associations with mental health distress and interpersonal relationship difficulties in adulthood. As mandated reporters responsible for the well-being of children, it is incumbent on practitioners and clinicians to assess the presence of sibling aggression. When working with adults, name the experiences so that the harmed no longer feel alone: sibling aggression and abuse are not the same as harmless rivalry. We cannot continue to undermine the significance of aggressive and abusive sibling relationships.