This paper reports on a study of Chinese parents' involvement in their children's heritage language (HL) development during the COVID-19 lockdowns in the UK. Involving seven transnational families, we examined the roles parents played during the online learning sessions and the factors shaping their involvement. Employing a netnographic approach, this study incorporates online classroom observations, semi-structured and focus group interviews with parents, and analysis of their Instagram posts. The study underscores the critical role of parental involvement (PI) in enhancing children's HL education, offering insights into distinct parental roles, including as emotional supporters, co-educators, teaching assistants, and technical supporters. The study introduces a three-dimensional PI model within the framework of family language policy (FLP), enhancing our understanding of FLP by concretely manifesting what, how and why parents get involved in their children's HL development. This study contributes to the discourse on PI and FLP, shedding light on the evolving roles of parents and the complexity of their involvement during the unique circumstances of the pandemic.