Kikuchi Mari

ABSTRACT Stepfamilies are increasingly prevalent worldwide; however, research on non‐Western stepfamilies remains limited. This study examines stepparenting, parenting behaviors, stepcouple relationships, and biological parents' co‐parenting quality in Japan, exploring their impact on the psychological adjustment of emerging adults (EAs). The sample included 421 Japanese EAs (aged 20–29) raised in stepfamilies with a resident biological mother and stepfather and a nonresident biological father. Using latent profile analysis, we identified four relationship patterns: Residence‐Centered (37.8%) with strong resident mother–stepfather ties, Inclusive (15.9%) with positive bonds across all parental figures, Inter‐household Ambivalent Loyalty (22.8%) with an ambivalent nonresident father bond and biological parents' conflictive co‐parenting, and High Stepfamily Conflict (23.5%) with frequent residential stepfamily conflict. The latter two profiles were associated with low self‐esteem, high depression and anxiety, and increased aggression. Similar patterns in Western studies suggest that the key aspects of stepfamily functioning may be shared across cultural contexts. Our findings suggest that balanced parental involvement and positive stepparent relationships may influence stepfamily adaptation. Providing effective support for stepfamilies requires assessing the entire family system—including nonresidential biological parents—rather than focusing solely on individual relationships. Positive parenting and connections are important; however, we found that differences in adjustment were more strongly linked to negative relational features. Hence, interventions that reduce these negative dynamics may benefit families facing considerable difficulties. Clinicians should attempt to deepen their understanding of what does and does not work in stepfamily settings.