The evolution of de facto relationships in Brazil: from concubinage to unmarried unions.

This article analyzes the modernization of family law by examining the evolving legal recognition of marriage and informal relationships, with a focus on selected jurisdictions in Western Europe, the USA, and Latin America, particularly Brazil. It highlights Brazil’s distinctive legal approach to "stable unions"—unmarried partnerships legally equated with marriage—characterized by the absence of cohabitation as a necessary criterion and the emphasis on the couple’s public intention to form a family. The study traces parallels between contemporary de facto unions and classical Roman marriage, which was based on mutual consent and affectio maritalis rather than formalities, contrasting with the formal, contractual model influenced by the Catholic Church. The article also discusses the legalization of same-sex marriage and civil unions as part of broader social and legal transformations that promote equality, human dignity, and diverse family configurations.