Using data from a statewide education project for adolescents (N = 736), this study explored family structure of youth in two-parent families and their influence on coping, sexual activity delay, and substance use. Although research in this area has tended to define family structure by the parent–child relationship, this study emphasized variations in family structure based on sibling relatedness. Results indicate differences when examining "traditional" classifications, as well as classifications based on half-sibling presence, such that those in nuclear families and those without half-siblings are advantaged over other groups. Using groups based on a combination of family structure and half-sibling presence, differences were found between youth in nuclear families and step-nuclear hybrid families (biological and stepchildren). Biological and stepchildren in step-nuclear hybrid families did not significantly differ on any measure. A race by family structure interaction effect was seen for measures of coping. On average, differences were seen for European Americans but not for African Americans.