Sibling sexual offending has received limited empirical attention, despite estimates that approximately half of all adolescent-perpetrated sexual offenses involve a sibling victim. The present study addresses this gap by examining male adolescent sibling (n = 100) and nonsibling offenders (n = 66) with regard to maltreatment histories and scores on two adolescent risk/need assessment instruments, the ERASOR and YLS/CMI. Adolescents who sexually abused a sibling, versus a nonsibling, were more likely to have histories of sexual abuse and been exposed to domestic violence and pornography. There were no group differences on ERASOR and YLS/CMI scales. This study adds to the limited discourse on sibling sexual offending and the larger literature on the heterogeneity of adolescents who have sexually offended. (Published Abstract)