There are significant nomothetic, differential, and idiographic domains of human development. We suggest the usefulness of efforts to understand human development in regard to specific facets of development—for instance, relationships within families with adolescent children—beginning with a focus on the specific, idiographic attributes of individuals. Using these relationships as a sample case, we provide a brief history of the study of the development of these relationships, and we explain the role of models derived from relational developmental systems metatheory in framing contemporary research about this development. We describe some of the nomothetic, differential, and idiographic features of adolescents and families, and we explain the methodological features of a truly developmental approach to measuring the development of mutually influential adolescent↔family relationships. Finally, we discuss the importance of including idiographic‐based information along with nomothetic or differential information in efforts to optimize adolescent–family relationships.