The main goal of this paper is to investigate and model the impact of genetically close relationships between languages in contact situations and to describe the consequences for bilingual speakers living in bilingual communities. Both Muysken’s concept of “congruent lexicalization” and Myers-Scotton’s definitions of “composite matrix languages” will be evaluated and an outline of a code mixing hierarchy designed to achieve a better understanding of convergence processes will be proposed. The main source of the data is an ongoing research project on “Variation in Multilingualism on the Faroe Islands”, supplemented by other parallel data from the German-Danish border region and German vernaculars. The results of the data analysis strongly suggest that, in the long run, code mixing is inevitable, preconditions being (balanced) bilingualism and the frequent alternating use of the two contact languages/varieties.