Substantial research concludes that most Americans want to have “at least 1 boy and 1 girl,” yet few have empirically explored what drives this preference. The author used nationally representative data from the National Survey of Families and Households (N = 5,544) and generalized ordered logistic regression to evaluate 3 potential psychosocial frameworks motivating the mixed-sex ideal using gender and family attitude variables. The results supported a “separate spheres” ideology, through which parents may view the interests, traits, skills, and roles of boys and girls in families as very different. Second, the results supported a rational choice orientation, whereby achieving this goal maximizes having a variety of needs met in old age. Third, the desire for 1 boy and 1 girl may be motivated by its symbolic capital as a status marker, representing the image of a “balanced,” ideal family. Based on beliefs about the nonsubstitutability of boys and girls, this ideal represents a form of gender inequality that persists in families.