Siblings playing in bed at home

(© djile -

COVENTRY, England — “He hit me first!” Where do bullies learn to be bullies? Look no further than under the roofs of many homes, especially those with three or more children. A new study shows that kids with more than one brother or sister are more prone to sibling bullying. The most likely perpetrators: firstborns or big brothers. The most likely victims: younger sibs of either sex.

Researchers at the University of Warwick wanted to know what causes siblings to pick on one another. They studied different elements that might play a factor — things such as parenting styles, family structure, early social interactions and children’s temperaments.

“Sibling bullying is the most frequent form of family violence and it is often seen as a normal part of growing up by parents and health professionals,” says lead author Dieter Wolke, PhD, in a release by the American Psychological Association. “But there is increasing evidence that it can have long-term consequences, like increased loneliness, delinquency and mental health problems.”

Researchers accessed data from a study of 6,838 British children born in 1991 or 1992 and their mothers.

For purposes of the study, sibling bullying came in three forms: psychological (saying hurtful things), physical (hitting, kicking or pushing) or emotional (leaving a sibling out or spreading lies or rumors about them). Children fell into one of four categories: victim, bully victim (both perpetrator and victim), bully or not involved.

The mothers were asked to report episodes of bullying in the household when the children were five years old. The moms then reported two years later how much time the children spent interacting with their siblings in crafts, drawing or other activities. Five years later, when they were 12 years old, the children themselves were questioned about bullying within the last six months. At this time, the children were also asked at what age they remembered the first sibling bullying event.

Researchers gathered other family facts, such as socioeconomic status, the mother’s marital status and the number of kids in the household. They looked into mental health and family conflict information. Finally, researchers gathered data about the children during their early years — temperament, mental health, IQ and social/emotional intelligence.

The results found that about 28 percent of the children participating in the study were involved in some sort of sibling bullying, usually in the form of sibling insults. Most of these kids were bully victims: both being bullied and dishing it out.

“Bullying occurs in situations where we cannot choose our peers, like in families,” says Wolke. “Siblings live in close quarters and the familiarity allows them to know what buttons to press to upset their brothers or sisters. This can go both ways and allows a child to be both a victim and a perpetrator of bullying.”

Two main factors were found to predict bullying by middle childhood: family structure and gender.

“Bullying was more likely to occur in families with three or more children and the eldest child or older brothers were more often the bullies,” says co-author Slava Dantchev. “Female children and younger children were more often targeted.”

The authors think bullying is a byproduct of competition for diminishing resources in larger families. Whether the children want material things or parental attention or affection, there simply is not as much to go around. Instead, they turn to dominance to acquire whatever it is they feel they’re losing out on.

The study showed no evidence that either marital or socioeconomic status matters to sibling bullying.

“Sibling bullying does not discriminate,” says Wolke. “It occurs in wealthy families just as much as lower-income families, and it occurs in single-parent households just as much as two-parent households.”

Study authors hope these findings will alert parents to potential problem areas as they grow their families.

“It will be important for parents to realize and understand that resource loss can affect an older child,” Wolke adds. “It is a good idea for parents to manage this from the beginning by spending quality time with their firstborn or older children and by involving them in caring for younger siblings.”

The green monster under the bed may be a case of sibling jealousy. Wise parents will tame sibling rivalry by addressing it early on.

The study was published in the February 14, 2019 online journal Developmental Psychology.

About Terra Marquette

Terra is a Denver-area freelance writer, editor and researcher. In her free time, she creates playlists for every mood.

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1 Comment

  1. Brooke says:

    I am female. My brother is 7 years older than me and bullied me my whole life — it was never mitigated. I recall my mother caring more about a one-time bully of my brother’s at his bus stop, but his repetitive physical and emotional abuse resulted in questioning: “What did you do to upset him? Boys are easier to raise. My sisters were mean to me but my brother wasn’t. Therefore, I don’t trust you.” We are adults and with indifference, I still observe his weaponized silent treatments, competitive nature, and jabs.