Research into Family Language Policy (FLP) focuses on language planning by and among family members within home spaces. In this study we gather data from multilingual young adults with different backgrounds across Mexico through an online questionnaire. We use a trajectory approach to look at how FLP changes over time and space from the perspective of young adults. Our data provides a diversity of young adult perspectives on the construction of linguistic trajectories, their relationship with the interventions, practices, and ideologies in the negotiation and emergence of FLPs, as well as how young adults are, or are not, using multilingual resources in digitally mediated family communication. Our findings show the dynamism of FLP over time and space, the diversity inherent in multilingual FLPs in Mexico, and how questions of mobility, generational differences, orality vs. literacy, digital access, globalization, and neoliberalism impact linguistic trajectories and FLP in Mexican multilingual young adults.