Analyses of fratricide rates based on national homicide data have provided some general information pertaining to offenders and victims of sibling homicide but are limited by data constraints to examining a few major variables. Exploring fratricide from a forensic psychiatric perspective could uncover other related factors and provide insight into why some individuals murder their siblings. In a retrospective study of data from coroners' files on domestic homicide pertaining to individuals killed by their siblings over a 10-year period in Quebec, Canada, we identified several specific offender and victim characteristics and circumstances surrounding offenses. The impact of mental illness and substance abuse on fratricidal behavior is indicated, underscoring the importance of identifying existing psychopathology. From a forensic psychiatric perspective, we identify characteristic patterns and discuss potential dynamics operating in fratricide. We raise some issues relevant to treatment and prevention, including the fact that most cases are alcohol-related, impulsive, and unpredictable until the moment they occur.