Nearly 80% of U.S. children grow up with a sibling. For many, brothers and sisters are life companions, close confidants and sharers of memories. But siblings also are natural competitors for parents’ attention. When brothers and sisters view parents’ love and attention as limited – or lopsided in favor of their sibling – rivalry may ensue.

Rivalry can motivate children to develop unique talents, abilities – such as in academics, sports or music – and other characteristics to gain their parents’ attention. Sometimes, however, rivalry can lead to jealousy and bickering – and too much of it can lead to aggression, bullying and even abuse and violence.

We are researchers who focus on sibling dynamics, parenting and mental health. Conflict among siblings is widely viewed as normal but, in the past decade, a new body of research consistently shows that sibling aggression and abuse are far from harmless – and can have lifelong repercussions.

Overlooking aggression

Aggressive behavior is characterized by an intent to cause harm, including physical pain and humiliation. Many behaviors between siblings fit this definition.

In 2013, using data from over 1,700 U.S. children, we found one-third of children under age 18 experienced physical, property or psychological sibling victimization in the previous year. In fact, sibling aggression is the most common form of family violence, with more children victimized by a sibling than by a caregiver. It’s a form of family violence not talked about, despite its ubiquity.

Great efforts have been aimed at reducing peer aggression, better known as peer bullying. The negative consequences of peer bullying are widely recognized. But a 2015 survey of 4,000 American children showed more are victimized over the course of a year by a sibling (21.8%) than by a peer (15.6%).

When peer bullying occurs, parents want it stopped – and experts encourage parents to talk with their children about what happened. Corrective action can include helping the bully develop understanding and empathy.

Yet, when the very same aggressive behaviors are displayed by siblings, they are typically dismissed by parents and even by the victimized siblings themselves. In fact, victim blaming often occurs, in which the victimized sibling is faulted for angering the abusing sibling or being overly sensitive.

Confusion about the difference between rivalry and sibling aggression prevents people from recognizing it. Aggressive behaviors, such as pushing, hitting or breaking cherished personal items, go beyond mild conflicts or fleeting bickering. But parents often rationalize aggressive sibling behavior – it’s just rivalry, it’s normal, no one got hurt. Sometimes adults even think it’s good for kids’ development to deal with aggressive behavior – that it makes them tougher.

For some, sibling aggression can be chronic and cross over to sibling abuse, which can leave physical or psychological injuries. Abuse involves objects, weapons, multiple tormentors or sexual assaults. About 4% of U.S. children report that during incidents in which their sibling beat, kicked or punched them, they sustained an injury or a weapon was used. A widely held view is aggression between siblings cannot be abuse. But for a surprising number of children, it is. This false belief has led to many suffering in silence.

Long term effects

Sibling aggression is linked to worse mental and physical health across the life span of the perpetrators and victims. Both experience higher rates of depression, substance use, delinquency and sleeplessness. Additionally, data shows just one incident of victimization at the hands of a sibling is linked to worse mental health in childhood and adolescence.

Experiences of sibling aggression also influence other relationships. Parent-child relationships can suffer. Some victims may become estranged from their sibling and parents. Additionally, sibling aggression and victimization behavior is often reflected in peer and dating relationships.

Origins of sibling aggression and abuse

The cause of sibling aggression can be rooted in family dynamics. Parents may model negative behaviors that are then repeated by children.

Our research found parental conflicts, violence and harsh parenting are all associated with sibling victimization. In another study, we showed family adversity – such as job loss, illness and death – was also associated with sibling aggression and abuse.

Certain personality traits, such as low empathy and anger, are also associated with being aggressive toward a sibling.

Prevention and intervention

Parents often want simply to stop the behavior and move on – or ignore it. However, this is a missed opportunity for teaching important social skills. To help children have positive relationships in their lives, parents should teach how to navigate conflicts in a healthy way.

When aggressive behavior occurs, parents should immediately interrupt it. Without taking sides, parents can help their children from a young age learn skills that lessen aggression, such as listening, seeing another person’s perspective, managing anger, negotiating and problem-solving. These important skills reduce destructive conflict and are associated with better mental health. They also potentially stave off aggression in other kinds of relationships.

In cases of sibling abuse, teaching siblings conflict resolution skills is not appropriate. Engaging in mediation may further victimize the targeted child when there is a power imbalance and potential or actual serious harm present. Being victimized and abused is not a form of rivalry; it requires the family to seek help from a mental or physical health professional.

Research shows it’s time to change the commonplace idea that aggressive sibling dynamics are harmless. Caregivers should take these behaviors as seriously as they do peer bullying or other forms of family violence. Addressing sibling aggression and abuse can improve children’s mental and physical well-being – as well as the quality of their relationships, both inside and outside the family.

Corinna Tucker receives funding from Louis and Anne Abrons Foundation.

Tanya Rouleau Whitworth works for the Sibling Aggression and Abuse Research and Advocacy Initiative (SAARA), which receives funding from the Louis and Anne Abrons Foundation.