This study examined the power of nonshared environment to differentiate adolescent monozygotic twin development and the extent to which this power varied across social structural contexts. Findings indicated that differences in maternal closeness, teacher bonding, and religious participation differentiated twins on emotional distress. Family income was the strongest moderator of these relations. In some groups, one twin's emotional distress was also associated with the other's familial and extrafamilial relationships. (Author/KB)