Using data from the 500 Family Study, this study examines how adolescents contribute to their families' social capital. An instrumental variable model reveals that adolescents' social involvement has a positive effect on social support from sources outside the family, suggesting that parents connect to other parents in the community through their children. This finding provides an interesting revision to Coleman's model of social closure. It indicates that rather than being solely the outcome of parents' investments, the creation of social capital is a process also mediated by the children themselves, who can act as motivators of network building for their parents. (Contains 3 tables, 1 figure and 3 notes.)