When Bullying Begins at Home

Why does sibling bullying occur and what can parents do about it?

Posted May 15, 2019

Bullying, in all its forms, can be emotionally devastating for anyone who experiences it. But what happens if the bullying is taking place right at home?

An estimated 85 percent of all children grow up with at least one brother or sister, so sibling relationships can can play an important role in shaping a child's mental and emotional development, not to mention establishing bonds that can last a lifetime. But the quality of these relationships often vary widely and, even in the best of circumstances, can mean considerable emotional tension at times. Researchers have long established that friction between siblings can lead to various behavioural and emotional problems in children and adolescents. And these problems can extend well into adulthood.   

This is especially true for sibling bullying, often defined as "repeated aggressive behavior between siblings intended to inflict harm." Such bullying can take many forms including physical abuse (i.e., hitting, kicking, or pushing), psychological abuse (saying deliberately hurtful things),  social sabotage (spreading rumours or telling lies about the siblings), or vandalism against a sibling's possessions.   

Often motivated by a real or perceived power imbalance or complaints of differential treatment, sibling bullying is the most frequently occurring form of family violence. Reported estimates of sibling bullying across childhood and adolescence range from 15–50 percent with victimization rates frequently peaking between the ages of two and nine.  

Unfortunately, sibling bullying is frequently ignored by parents, teachers, and health professionals, many of whom dismiss these reports as a "normal" part of growing up. But there is now increasing evidence that children victimized by their siblings can be prone to  long-term problems including delinquency, social isolation, depression, substance abuse, and other mental health issues.  Preventing these problems means identifying potential risk factors that can lead to sibling bullying and finding real  solutions for at-risk families.

So, why does sibling bullying occur? Based on the peer-bullying literature, children and adolescents affected by bullying are usually classified into three main groups — victims, bullies, or bully/victims — depending on how their behaviour feeds into the victimization cycle. While each bullying group has its own set of unique predictors, numerous theories have been put forward to explain why bullying occurs. 

This includes evolutionary theories focusing on the competition between siblings for the limited love, attention, and resources that parents can provide. For example, Resource Control Theory (RCT) proposes that sibling aggression occurs when siblings have different interests which force them into conflict over limited family resources. Since older siblings are bigger and stronger, this gives them a natural advantage in bullying their younger counterparts. Certainly aggression seems to be more common in households with more children, more brothers, or involving older and firstborn siblings intimidating younger siblings.   

On the other hand, there are social learning perspectives suggesting that aggression is learned through social modeling and how aggressive behaviours are reinforced. Children who are exposed to direct or indirect aggression within the family are more likely to imitate this behaviour when interacting with siblings. Research into domestic abuse and parenting has shown that children who witness parental violence or who experience maltreatment themselves are consistently more prone to sibling aggression as they grow older. But this isn't necessarily limited to family violence. Children who have been bullied by their peers also seem more inclined to become aggressive against siblings.   

Early childhood experiences, including the quality of the relationship that children have with their parents influences how children interact with others as they grown older. Children who learn that coercing younger siblings is an effective way of getting what they want will continue in this kind of behaviour if left unchecked by parents or guardians. Even basic differences in temperament and physical development (such as with children who are physically larger than others) can increase the risk of bullying among siblings.

Unfortunately, despite the increased awareness of the impact that bullying can have on children, sibling bullying has been largely neglected by researchers up to now. But a comprehensive new research study published in the journal Developmental Psychology may help change that. For their research, Slava Dantchek and Dieter Wolke of the University of Warwick used data from the Avon Longitudinal Study of Parents and Children (ALSPAC).   

Conducted by the University of Bristol, ALSPAC is one of the largest prospective studies into child development in the world. Beginning in 1991, ALSPAC researchers recruited more than 14,0000 pregnant women who were subsequently followed with their partners and children over the next two decades. This included annual assessment of all the 14,0000 children in the study using face-to-face interviews and questionnaires.   

For their research, Dantchek and Wolke selected 6838 children who completed a screening questionnaire including items on sibling bullying and victimization. All of the children had an average age of twelve years. They then completed an bullying questionnaire in which they were asked whether they bullied or were victimized by a sibling within the previous six months. For the purpose of the study, bullying was defined as "when a brother or sister tries to upset you by saying nasty and hurtful things, or completely ignores you from their group of friends, hits, kicks, pushes or shoves you around, tells lies or makes up false rumours about you." Along with bullying data, additional information for each child was collected including family characteristics, information about the parents, early social experiences, and individual differences (such as temperament).  

According to results, 28.1 percent of the nearly 7000 children studied reported experience with sibling bullying, whether as a victim or a victimizer. While psychological sibling bullying (such as name-calling) tends to be the most common, other kinds of bullying were reported as well. For example, about 31 percent of the total sample reported being physically abused (e.g., hit, kicked, pushed, or shoved) while 6.4 percent reported having their possessions stolen or vandalized. The average age for both bullying and victimization was about the same (around 8 years).   

The largest percentage (11 percent) admitted to being bully-victims (experiencing sibling bullying as well as victimizing younger siblings). Children reporting being victims alone accounted for 9.7 percent of the group (7.1 percent were bullies alone). Males bullied their siblings much more frequently than females did while female children with older brothers often reported being victimized. Other predictive factors linked to sibling bullying included:

  • Birth order. Overall, firstborn children (particularly firstborn males) were reported as being more likely to bully younger siblings.   
  • Family size. Growing up in households with more children also predicted sibling bullying.
  • Parenting. Children from households with suboptimal parenting (lack of parental warmth, family conflict) seemed more prone to sibling bullying while good parenting practices acted as a protective factor.
  • Peer victimization. Being victimized by age peers outside the home seemed to increase the risk of becoming a sibling bully or bully-victim.
  • Early experience of bullying. Being victimized when five or younger significantly increased the risk of bullying siblings at a later age.
  • Individual differences. Children experiencing behaviour problems, poor social cognition, and antisocial behaviour seemed more prone to becoming bullies or bully-victims. Interestingly enough, having high self-esteem appears to help protect against bullying behaviour. 

While none of these factors can predict sibling bullying in themselves,  it's important to recognize that they can be used as "red flags" when looking at why some children are experiencing emotional or behavioural problems.   

Though this study has significant limitations, including the fact that these results are based solely on self-report, these results confirm that sibling bullying is something that often occurs behind "closed doors" with parents or teachers being completely unaware of what is going on.  Still, it seems significant that sibling bullying most often occurs in families with more children or with older males, possibly due to a need for social dominance (as predicted by evolutionary theories of aggression). More research is definitely needed to examine how sibling bullying can affect children and what parents can do to try to protect younger children.    

Even though we are becoming more aware of the often devastating effect of peer bullying on children who are victimized, many parents are still turning a blind eye to the bullying that may be taking place under their very roof. Recognizing that such bullying can occur and that the consequences can be just as severe as the other forms of bullying peers can be essential in helping prevent mental health problems in children and adolescents. 

Just as importantly, parents need to take reports of sibling bullying seriously. It isn't a "normal part of growing up" and children deserve to be protected, both from risks outside the home as well as inside.


Dantchev, S., & Wolke, D. (2019). Trouble in the nest: Antecedents of sibling bullying victimization and perpetration. Developmental Psychology, 55(5), 1059-1071.

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