The primary goal of this research is to increase the goodness-of-fit between thetheoretical tenets of family systems theory and quantitative methods used to test systemshypotheses. A family systems perspective is applied to two specific research questionsconcerning family influences on adolescent development: To what extent are familial risk andprotective factors for psychopathology and competence shared or not shared by siblings and aredifferent family relationship patterns associated with optimal adolescent adjustment innondivorced and remarried families? Multirater and multimethod data from a national sample of516 nondivorced and remarried families from the Nonshared Environment and AdolescentDevelopment (NEAD) project were examined using a combination of cluster, factor, andregression analyses. Results indicated that the effects of an individual relationship on adolescentadjustment is moderated by the larger network of relationships in which it is embedded.Evidence for nonshared familial processes in predicting adolescent psychopathology was alsofound but only in a subset of families, and the mechanisms of influence were neither main effectsnor linear, as has been assumed by research to date. Results are discussed in light of familysystems models of relationship influences on development. These results illustrate how familysystems theory provides a specific example of contextualism as regards the development ofpsychopathology in adolescence.