Research on multilingualism in the home has approached the family as a fixed unit thus neglecting the dynamic view of the family and its intersection with family language practices. The present study aims to address this gap by focusing on Russian-speaking mothers in Finland who have raised their children bilingually in single-parent as well as in dual-parent families. Russian speakers are the largest minority language group in Finland, and their number is constantly growing. The current study is a contribution to the research on family language practices in the Finnish context. It examines the nexus of shifts in family configurations and language practices and explores how the dynamic changes in family constellations shape language practices in four families. The study reveals that creating new kinships leads to shifts in the language practices of the peripheral family members and that forming voluntary kin can expand heritage language use and enable an overhearer and bystander role for children. Non-residential family members expand the family's linguistic repertoire and support the legitimacy of already established practices. Being sole caretakers enables mothers to encourage language practices that they consider beneficial for their children without encountering any resistance from other family members.