The paper seeks to explore senior cohousing as an emerging legal phenomenon standing at the crossroads between private autonomy and social solidarity. Demographic ageing and the erosion of traditional family structures have raised new issues for European legal systems to cope with, challenging conventional frameworks governing housing, care, and interpersonal relationships. Drawing on comparative analysis, the study explores how Spain, France, Germany, and Italy articulate legal solutions to solidarity-based cohabitations among older people, revealing divergent models that variously rely on contractual autonomy, statutory protection, or hybrid regulatory schemes. Foreign experiences – from Catalonia’s mutual-aid cohabitations and Valencian collaborative housing to France’s Housing, Development, and Digital Law and Germany’s ‘community of responsibility’ – highlight the growing tendency to connect occupancy rights not merely to property titles but to the social function and status of cohabitants. The paper argues that senior cohousing requires recognition as a distinct legal formation grounded in voluntary, non-familial solidarity, demanding regulatory solutions capable of stabilizing housing arrangements while preserving individual autonomy. Ultimately, the research aims to show that contemporary legal systems are gradually shifting from family-centred notions of solidarity toward more flexible, community-based models, offering a framework for rethinking the governance of ageing, housing, and care in contemporary societies.

The paper examines senior cohousing, a housing model in which older people live in private units while sharing spaces, services, and mutual support. It argues that this model can promote active ageing, autonomy, dignity, and social inclusion, but only if the law provides enough stability to the living arrangement. The main legal issue is whether the solidarity-based purpose of senior cohousing can justify special rules on the right to occupy the home. The paper starts from Italy, where specific national guidelines are still being developed, and compares the legal approaches of Spain, France, and Germany. Spain shows a cooperative model based on stable rights of use and anti-speculative rules. France offers stronger statutory protection for older tenants and promotes intergenerational solidarity. Germany relies more on private contracts, showing how solidarity can arise through carefully designed legal relationships. The paper concludes that senior cohousing cannot be fully governed by ordinary property or family law alone. A new legal model is needed, one that balances private autonomy with social solidarity, protects older people from loneliness and housing insecurity, and supports stable, meaningful communities in later life.