This session explores the importance of HL acquisition evidence from the perspective of non-specialists in acquisition who are working to understand how acquisition evidence needs to inform our work on a particular set of heritage languages, namely Germanic HLs in contact with English. We look here at connections to theory, in both synchronic and diachronic realms. These languages generally show lower levels of linguistic distance than most other settings discussed at this institute, in the sense of typological proximity/distance (Putnam et al. 2018) and the communities are typically elderly. We draw data from bilingual sound systems, inflectional systems, and clause structure, with an eye to how such pieces fit into a larger whole of bilingual grammar and linguistic change.