While adoptive family research has increased, most has focused on childhood and adolescence. Despite the known importance of parent-adolescent relationships drawn from the general population, we know little about how adoptive family relationships change or remain the same as adopted adolescents enter young adulthood. Utilizing the Sibling Interaction and Behavior Study, the purpose of this study is to build upon previous research to explore differences in conflict, closeness, and relationship quality between adoptive and nonadoptive families during the transition from late adolescence into young adulthood. Self-report and independent observations were collected from children, mothers, and fathers at late adolescence (14.50–18.49 years) and young adulthood (18.50–22.49 years), and analyzed using within subjects repeated measures. While adoptive family dyads had lower relationship indicators compared to nonadoptive family dyads, similar trends over time occurred for both family types. Using individuation theory, we suggest individuation occurs for both types of families, with adoptees facing unique additional challenges during this process, including integration of adoption status, adoption communicativeness, adoption information seeking, and relationship with birth parents as possible influences in this process.