Sisters, brothers, and delinquency: evaluating social influence during early and middle adolescence.

Although a number of studies have shown that brothers are highly correlated for delinquent behavior, much less research has been conducted on sisters. We propose that sisters, like brothers, show notable similarity for delinquent behavior, and also promote each other's delinquency through direct interaction. We examined these issues in 164 brother and sister pairs studied over a 4-year period (from early to middle adolescence) in a study of intact families in the rural Midwest. Sibling similarity for self-reports of delinquent behavior were highly correlated for both brothers and sisters. Conditional effects of high levels of hostile-coercive sibling relationships and older sibling delinquency predicted younger sibling delinquency in both brother and sister pairs. For brothers, conditional effects were also detected for high levels of warmth-support, in contrast to sisters. The conditional effects of older sibling delinquency and relationship quality were shown to predict change in younger sibling delinquency through adolescence. The results add to a growing literature on sibling effects as well as theoretical models that emphasize the role of social interaction between siblings as a risk factor for the development of delinquent activity in adolescence.