Who can be an adopted parent in Brazil? Who can be adopted? The present thesis aims to present a study on gender binarity, based on the analysis of the adoption institute of Brazil s Family Law, using it as a key to enter the cisheteronormative matrix, in order to verify how the constructions of subjectivity are crossed by the established norms. The idea investigated is that the Law would not only be a reflection of society, but that it would also constitute, through its normative field, a matrix of naturalization and subjugation, a gender power. Thus, initially the ideas of gender binarity and cisheteronormativity are characterized, with the analysis of their overlap with the affects, taking the queer theory as reference, through the works of Judith Butler - influenced by the theories of Spinoza and Foucault. With this, the aim is to understand how the binary system of sexual categories that each individual is determined at birth affects us. Then, the appropriation of affections by Law as a gender power is specifically analyzed, showing how, through the principles of affectivity and socio-affectivity, the ideas of socio-affective filiation and parentality and the influences of Canon and Roman Laws, the structure of a gender binary was constructed in the adoption institute of Brazil s Family Law. Based on this observation, the research follows with the study of the genealogy of this institute and the fictions created from it, such as the National Adoption Register, observing its conformation to a structure that, since its genesis, has been gendered and sexualized, aiming to maintain a binary adoption. By following a qualitative methodology, the thesis has a critical study of the speeches contained in eight Family Law manuals, builders of this field of Law in Brazil. It examines the uses that these works, published between 2015 and 2020, attribute to the words gender and adoption, in order to understand the (re)creation of the mechanisms of the gender binarity. In addition, the research performs a documental analysis of the jurisprudence and legislation of adoption and the institutes related to it, as well as an empirical investigation through participant observations in seven meetings of Adoption Support Groups and conversations with operators of the legal system in cities of Rio de Janeiro. With the exam of the narratives of the meetings, it was possible to observe people s relations with gender binarity in issues involving adoption. On the other hand, analyzing the discourse of five legal professionals, it was understood how the categories gender and affection are appropriate and operationalized in order to keep in operation, through these actors, the mechanisms of the cistem. Finally, using Civil Constitutional Law as a lens, the thesis reaches the result that Law constitutes a structure that imposes, in its normativity, a process of genderfication and sexualization of the subjects to which it aims to represent and attribute legal effects. For this reason, the work is committed to serve as a tool of social justice, assisting in the agency of subversive performances; recognizing them, to help them leave the precarious zone which they are subjected to.