Birth order and fratricide: an evaluation of Sulloway's hypothesis.

Sulloway (1996) suggested that older siblings were more likely to be fratricidal than younger ones. Our data, based on 113 case studies found in the psychiatric, psychological and criminological literature since 1959, confirms his hypothesis. In 72 out of the 92 cases (78%) where age could be determined, the aggressor was older than the victim. The same held true even when the age of aggressor, sex of aggressor and victim, presence or not of a blood tie, and presence of one or more victims are taken into account. Surprisingly, most of the aggressors in our sample were under the age of 18 years. Also, first-borns were more often the aggressor than the victim. This result seems to confirm the Adlerian theory of dethronement. Some suggestions and hypotheses are advanced for future research to improve our understanding of this phenomenon.