This chapter focuses on the subset of black-white couples who were parents to examine: expectations of their child's racial classification; how parents categorized their children after birth; and the implications for eligibility for university affirmative action. Carioca parents often expected to have black children due to mixture with a black parent. However, after birth, a child's phenotype determined the category they fit into, such that a child could be white, black, or less commonly, “mixed." Affirmative action did not cause Carioca parents to waver in their assessments of their children's race; white children were ineligible. Angelino parents described their child's race as additive: both black and white. They maintained the biracial categorization before and after their child's birth, regardless of the child's appearance. In light of affirmative action eligibility, Angelino parents became more flexible in their assessment, emphasizing blackness if they considered it advantageous. Sometimes they understood “biracial” as a unique minority status adding to institutional diversity. This chapter demonstrates parents' part in the social construction of new ethnoracial boundaries, strengthening of pre-existing ones, and the effect of public policy on understandings of ethnoracial boundaries.