Fratricide: Multifactorial Risk Factors Across Genetic, Familial, and Social Domains

Fratricide (killing of one's brother) is a rare but extreme form of family violence. Research identifies converging risk factors across domains:

Biological and Genetic

• Candidate gene associations (e.g., MAOA low-activity variants, 5-HTTLPR) — interact with environment.
• Neurodevelopmental: prefrontal cortex dysfunction, impulse control deficits.

Perinatal and Developmental

• Advanced maternal age → increased de novo mutations, pregnancy complications.
• Birth order: firstborns overrepresented in some studies (resource competition, parental investment shifts).
• Close birth spacing → heightened rivalry, resource dilution.

Family Environment

• History of domestic violence, child abuse, neglect — modeling aggression.
• Parental favoritism, comparison, unequal treatment.
• Poor supervision, chaotic household.

Sociostructural

• Poverty, neighborhood violence, limited opportunity.
• Cultural norms endorsing honor violence, male aggression.
• Access to weapons.

Psychological

• Psychopathy, conduct disorder, substance use, psychosis.
• Perceived injustice, humiliation, inheritance disputes.

No single cause; risk accumulates across levels. Prevention: early family support, conflict resolution, mental health access, firearm safety.