Prior research shows that participation within communities of practice shapes children's development of repertoires of practice--ways of engaging in activities within a cultural community. Families are a privileged community for learning because of the extensive time spent together, the intimate nature of family relations, and the importance of this time for learning before children enter schools. It is therefore important to explore how culture shapes children's learning in the family context. I seek to understand what the concept of family culture explicates about young children's learning through inquiry and how children participate in shaping family culture. Drawing on Nasir, Rosebery, Warren, and Lee's definition of culture, I explore how family culture serves as substrate--resources for interaction--that can be built, reified, and transformed in interaction. Using the analytical lens of Domain of Value (DoV)--constellations of valued purposes and practices associated with collections of phenomena--I present a case study of two families and how an understanding of a family DoV contextualizes moments of learning through inquiry. This analysis supports understanding how the contextual horizon traced through interactional histories sheds light on practices children draw upon when inquiring about their world with others. Through this analysis I explore how family culture serves as context for learning and how children shape that culture. By explicating the role of family culture on children's learning, this work contributes to understanding cultural variability. This work also pushes against monolithic representations of cultural communities and narratives of any singular "normal" developmental pathway. Finally, this work demonstrates the competence and brilliance of young children as they co-construct inquiry about their world, shape their family culture, and then connect to these cultural resources in new contexts.