This study proposes a family psychobiosocial model on gender differences in cognitive development. Specifically, the aim is to investigate how family biological, socioeconomic, and psychological factors predict child mathematics achievement (MAch) development. The data were obtained from the Millennium Cohort Study. Children's pattern construction scores collected at ages 5 and 7 years worked as MAch (n = 18,497). The predictors were family data collected when the children were 9 months. The results of path analyses for all students indicate that all three factors in the family psychobiosocial model play some roles in children's MAch development. Analyses for the female and male students separately reveal that girls' positive MAch development was significantly predicted by four psychobiosocial factors (fewer mother in-pregnancy alcohol intakes, more family income, higher mother education levels, and more mother cognitive stimulation); boys' MAch development is predicted by only one factor (higher mother education levels). The results support the psychobiosocial model as a whole. Family psychobiosocial factors, especially social factors, impact children's cognitive development more for females than for males.