This research explores family law in 20th century Brazil from the perspective of women’s rights. Women and men – as wives and husbands, mothers and fathers, daughters and sons – have precise, albeit changing legal roles, which depend upon contingent discussions about the social construction of gender, sexuality, masculinity and femininity. Across time, for instance, women in Brazil gained the right to vote (1932); the right to seek and accept job offers without prior consent from their husbands (1962); the right to divorce (1977); the right to work night shifts (1988); and, more recently, the rights to sue perpetrators for domestic violence (2006) and to enter into same-sex marriages (2011). Thus, I am interested in the legal and political relations between women’s rights and the architecture of Brazilian family law. My work asks: how have changing perceptions of gender roles, sexuality, and of proper femininity affected women’s rights and responsibilities in the familial domain? The family unit, as a legal entity, is a plastic and gendered social construct whose participants have specific rights and duties, so I see the changing architecture of families as a vantage point from which to comprehend disruptions, conflicts, and changes in gender assumptions as well as in women’s agency and capacity to intervene in the processes of law-making.