Youths of marginalized demographic groups frequently find themselves excluded from participatory discourses in school science. As a result, these students often decide early in their school careers that science is not "for them" and consequently infrequently pursue STEM careers. Efforts to increase diversity of STEM participation have included targeted informal learning experiences for young people from marginalized populations. However, these efforts are not always designed to explicitly support STEM identity formation--a construct closely associated with STEM career pursuit. In this study, we explore the connection between childhood informal STEM learning experiences of Hispanic/Latino students at a Hispanic Serving Institution, their identification with STEM, and the factors that contribute to their STEM identity (recognition as a STEM person and interest in STEM). Results show that talking about science with friends and family was the only informal learning experience associated with students' STEM identity or the factors contributing to STEM identity development. Moreover, talking with close family about science was more relevant to their identity formation than talking with extended family or friends. Implications discussed include the need for bridging science learning experiences with home culture.