This article provides a comparative analysis of the legal recognition and protection of cohabiting siblings in England and Wales, Catalonia, and Belgium, aiming to identify viable models for accommodating this relationship form. In England and Wales, there is no informal cohabitation regime, and siblings have been consistently excluded from major reform proposals in horizontal family law – despite early debates on their inclusion in civil partnerships. In contrast, Catalonia’s cohabitation relationships of mutual aid bind legal effects to informal cohabitation among siblings and other non-conjugal cohabitants, while also allowing them to formally enter these arrangements. However, the default rights attached to this status are far fewer than those granted to married or recognised conjugal couples. Belgium offers the most robust model, enabling siblings and other non-conjugal pairs to register as legal cohabitants. While its private law effects are limited, its status grants substantial tax and social benefits. The comparison is timely as England and Wales revisit cohabitation law reform. Excluding siblings from legal protection – whether through ascriptive or formal regimes – denies a group often engaged in caregiving both recognition and benefits. Experiences from Catalonia and Belgium demonstrate that including cohabiting siblings in future care-based reforms is not only possible but compelling.
Maine et al. (Mon,) studied this question.