This article provides a theoretically grounded critical analysis of how the Belgian and the Dutch legal systems are addressing new kinship formations through the production of new legal terminology. As Belgium and the Netherlands are at the forefront of legal recognition of minority sexualities and emerging forms of relatedness, statutory Belgian ‘co-motherhood’ and Dutch ‘duo-motherhood’ for ‘lesbian parents’ (both enacted in 2014) cast some light on how European state family laws and policy frameworks are likely to evolve vis-à-vis the multiplication of new family formations. After tracing the developmental trajectory of these new family law categories and their connection to ordinary language categories, the article claims that legal labels are hardly merely descriptive, for they exert contradictory effects of recognition, regulation, normalization and exclusion. By foregrounding the potential frictions between ‘kinship-in-action’ and ‘kinship-in-the-books’ and the possible drawbacks of top-down statutory interventions, the article contends that, when based on conventional family categories, legal kinship terminology runs the risk of foisting pre-given narratives upon emerging kinship formations, which would eventuate in the normalization of alternative realities. The article concludes by drawing a parallelism between partnership labels and parenthood labels and by advocating the need for deeper ethnographic research before new legal kinship labels are crafted.