Annotation. This article reveals the concepts of identity. The impact of incomplete families on the formation of gender identity in children with the subsequent formation of a marriage partner on the example of the girls from incomplete families. Single-parent family has an impact not only on the formation of identity, but also affects the mathematical ability, as in girls, and boys. Codeword: sexual identity, girls, boys, adolescents, ability, mental development, relations, single-parent family, a father, a mother, a social experience. In the modern world there is no clear definition of identity. According to E. Erikson's research, adolescents consciously try to synthesize previous experiences with personal obligations in order to resolve their emerging questions about the meaning of their own lives. It also acts as a psychological construct in adolescence, and the functionality of the individual in independent adult life depends on its correct formation. Personal identity is understood as a sense of identity or continuity of the Self, which is preserved despite environmental changes and individual development. It is also a process an individual’s awareness and experience of his gender – masculinity or femininity, physiological, social and psychological characteristics of his gender. The process of gender-role identification begins literally from the moment a child is born. In her research, J. Marcia notes that “self-determined” and “predetermined” girls and boys are the most resistant to group pressure; the highest level of gender independence and the lowest level of anxiety are found. Girls and boys in these categories are most often children of two-parent families, as a result of which they have higher moral reasoning, the ability to independently manage their own lives, adaptability, intimacy and the ability for cognitive introspection. According to most psychologists, the presence of both parents in the first years of a child's life play a decisive role in the development of masculinity in a boy, femininity in a girl and the further formation of heterosexual relationships in the future. Therefore, if during this period the child has to live without one of the parents, then the formation of gender identification may cause some difficulties if no other man or woman accepts assume the role of mother or father. The absence of a full-fledged family model, the participation of both parents in upbringing almost always leads to certain disorders in the mental and personal development of the child. According to most psychologists, when comparing the intellectual abilities of children from intact families and single-parent families, distinctive features in development This area of ​​the child begins to manifest itself most clearly at school age, when mental activity becomes most intense. To what extent do two-parent families and single-parent families relate to the formation of identity and school performance in adolescents? Indeed, according to Edmund Buri's research, young men have higher abilities in the exact sciences (mathematics), more developed abilities for spatial orientation, tend to think about a problem, their minds are directed more at things than at people. Girls, unlike boys, have more developed verbal skills, they have a much larger vocabulary compared to the opposite sex, they know how to operate with concepts, and are capable of quickly calculating a situation thanks to their well-developed natural intuition in general. They feel the nuances of interpersonal relationships more subtly. As a result of all of the above, it can be argued that a child needs to observe both parents in the family for full development, for the formation of his identity and the ability to communicate with both his own and the opposite sex. A child who is raised only one of the parents, has much less opportunity to get acquainted with different