This study examined older siblings' influence on their younger brothers and sisters by assessing the connections between youth's perceptions of sibling influence and sibling similarities in four domains: Risky behavior, peer competence, sports interests, and art interests. Participants included two adolescent-age siblings (firstborn age M=17.34; second-born age M=14.77) from 191 maritally intact families. Analyses revealed that second-borns' perceptions of influence were positively linked to siblings' reports of intimacy and temporal involvement, but not to reports of negativity. Further, sibling similarities were most evident when younger siblings reported sibling influence and when their older brothers and sisters reported high engagement, competence, or interest in a particular domain. Discussion focuses on the challenges of documenting sibling influence and the need to refine its measurement.