Background: The relationship between socioeconomic position and union formation has frequently been studied in majority populations. Despite the growing importance of minority groups in European populations and their often different patterns of union formation and labour market positions, variation in the socioeconomic preconditions for union formation by migrant background has hitherto received less attention.

Methods: Using longitudinal microdata from the Belgian Social Security registers, this paper studies whether the link between activity status and income on the one hand and coresidential union formation on the other differs between young adults of Belgian origin and second-generation migrants of Southern European, Maghrebi, and Turkish origin.

Results: Whereas socioeconomic preconditions for union formation are largely similar among men across origin groups, we find that second generation women of Turkish and Maghrebi origin are more likely to enter into a coresidential union from vulnerable or uncertain socioeconomic positions such as inactivity and unemployment compared to women of Belgian and Southern European origin.

Contribution: This study finds that the socioeconomic preconditions of coresidential union formation found among majority populations cannot be generalised to all population subgroups. Our results indicate that the extent to which population subgroups occupy a precarious socioeconomic position may impact how and to what extent decisions in other life domains depend on one’s socioeconomic position.