This study examines an on-going study of interactional strategies and measures in heritage language transmission in a family language policy (FLP) project in the UK. It explores how parents, children and members of the extended family use verbal resources to make sense of their everyday life, and how their language use is related to the development of their heritage language. Importantly, it focuses on interactional devices and features in family members’ daily casual conversations that contribute to heritage language maintenance and development. The study is situated in the transnational context of the UK, in which transnational families often engage in multilingual practices with their family members close and far via digital devices or face-to-face interactions. Involving two transnational communities in the UK, the Chinese and the Polish, the study focuses on the language practices of three families in each community. Data sources include recordings of meal time conversations, daily casual conversations, and skype/facetime family talk. Using family discourse as analytical framework, the study investigates linguistic features and discourse strategies that contribute to the interactional dynamics underlying ‘family talk’. In particular, the study explores how children and adults position themselves in moment-by-moment family discourse and how that affects heritage language learning. The findings contribute to FLP literature by examining how linguistic devices and discourse measures are imbedded in family life practices that play significant roles in heritage language development. The study contributes to minority language maintenance and development by exploring social and cultural functions of heritage language expressions. It enriches the field of FLP by exploring how family language ideologies are established through language socialisation.