Sibling Bullying and Abuse: The Hidden Epidemic
Sibling abuse is the most common but least reported abuse in the family. Prevalence is higher than spousal or child abuse combined with consequences well into adulthood similar to parent-child abuse. Up to 80 percent of youth experience some form of sibling maltreatment; yet, it’s been called the “forgotten abuse.”  Therapists also frequently overlook it. Usually, the perpetrator is an older child (often the eldest) exploiting the emotional dependence and weakness of a younger sibling. Girls are at greater risk of abuse, generally by an older brother. When a brother abuses a sister, it often involves physical or sexual abuse. Sisters abuse one another also.
Lack of Reporting
Under-reporting is predominantly due to societal denial of the seriousness of the problem. There is no definition of sibling abuse or laws governing it (except for some sexual abuse laws.) Resources for families are also lacking. Parents have no support and are misinformed. Many expect sibling conflict and fighting. Hence, they typically overlook abuse and confuse it with sibling rivalry. When they don’t protect the victim, it constitutes a second wound–first inflicted by the sibling, then by the parent.
Sibling rivalry and abuse are different. Squabbles, jealousy, unwillingness to share, and competition are normal sibling behaviors. Fighting between equals can be, too. Rivalry is reciprocal and the motive for is for parental attention versus harm and control. Rather than an occasional incident, abuse is a repeated pattern where one sibling takes the role of aggressor toward another who consistently feels disempowered.
Typically, an older child dominates a younger or weaker sibling who naturally wants to please his or her sibling. It’s often characterized by bullying. Unlike rivalry, the motive is to establish superiority or incite fear or distress. Intent and the degree of severity, power imbalance, and victimization element are all factors to be considered. Inappropriate parental discipline or ineffective attempts to respond to rivalry or abuse can compound the problem by the lack of consequences or by targeting one child. If a parent is overly strict or abusive, the perpetrator often vents his or her rage on the younger sibling.