Family has long been observed as an organizational unit consisting of relational structures that affect family members, their engagement with others, and their involvement beyond the family. This research identifies family relational structures that affect a sense of interpersonal agency denoted as autogenesis. Autogenesis is a model of interpersonal agency consisting of increasingly differentiated frameworks of relating to others in an interpersonally agentic way. The increasing differentiation encompasses both an increasing sense of interpersonal agency and a widening sphere of interpersonal engagement. Details regarding family from 16 largely unstructured interviews of college-age participants on the topic of interpersonal relations are analyzed to identify (a) general family relational structures by an autogenetic framework determined by rating the interviews for autogenesis using the Autogenetic Coding Manual and (b) specific family interaction structures by an autogenetic framework associated with the degree or level of autogenetic differentiation. Four family interaction structures were identified: physical and psychological support, variety of alternative or opposing perspectives, sibling and friend relationships, and support from chronological seniors. For study participants, the presence of 1 or more of these interaction structures of family organization is found to be associated with increased levels of autogenesis, that is, more elaborated interpersonal agency and expansive interpersonal engagement. The absence of these unadulterated family interactive structures is associated with decreased levels of autogenesis, that is, less elaborated interpersonal agency and less expansive interpersonal engagement. (PsycINFO Database Record (c) 2018 APA, all rights reserved)