There is ample scientific evidence for the importance of parental gender socialization in children’s binary gender development. Surprisingly, little is known about the role of parents’ own gender identity in the binary gender identity development of their children. Therefore, the present study investigated the association between parents’ and children’s binary gender identity (i.e., similarity to same- and other-gender individuals) in a sample of 142 Dutch families with a child between the ages of 6 and 12 years old. The Dutch context is characterized by relatively high gender equality. Both parents and their children answered questions about their similarity to same-gender and other-gender individuals. Generalized estimating equations revealed that parents’ same-gender similarity and parents’ other-gender similarity were positively associated with their children’s same- and other-gender-similarity, respectively. In addition, more other-gender similarity in parents was associated with less same-gender similarity in girls, but more same-gender similarity in boys. Parents who reported high similarity with both genders were more likely to have children who also reported higher similarity with both genders. These findings indicate that parents’ own binary gender identity is related in general and specific ways to their children’s binary gender identity development. Parents should be made aware of their role in children’s binary gender identity development. Yet, more research on different types of gender identity in parents and their children is necessary.