In the Inner Mongolia Autonomous Region (henceforth IMAR) of China, children of bilingual parents are increasingly becoming monolingual in the socially dominant language - Mandarin. Mongolian language, representing the unique culture and identity of Mongolian ethnic groups, is facing a decline in usage within the family setting. This case study investigates the Family Language Policy (henceforth FLP) and its interaction with mainstream and minority language education through observations, semi-structured interviews, and questionnaires with two distinct groups. Group 1 demonstrates the contemporary implementations and challenges of FLP among 5 bilingual parents and Group 2 offers the historical perspectives of 9 bilingual adults with their retrospective account of childhood language experiences. Through comparing the two groups, we identified the critical role of FLP in supporting the development of children's minority languages. We also uncovered challenges and inconsistencies that parents encountered in implementing FLP. These issues stem from a variety of factors, including economic, sociocultural, and political influences, as well as individual factors, such as expectations and language experiences from both parents and children.