Fertility motivations are at the forefront of the decision to have a child. However, the experience of raising sons and daughters constantly reframes couples' fertility motivations. We construct a four-dimensional analytical framework of fertility motivations. Using 2020 China Family Panel Studies (CFPS) data and Ordered Probit Model, we analyze the impact of children's gender composition on couples' fertility motivations. The results show that “Familyism” and “Economic Utility” motivations are more pronounced among husbands than wives. “Individualism” and “Emotional Utility” motivations are stronger among wives than husbands. There exists “Gender Equality Dilemma” in residents' fertility concepts. From the perspective of children's “gender-number” structure, among couples with the same type of structure, those with more children have a higher comprehensive score of fertility motivations. From the perspective of children's “gender-age” structure, having both sons and daughters reinforces traditional gender norms and increases satisfaction with sibling structures featuring an elder brother-younger sister dynamic. From the perspective of children's “gender-economic” structure, being economically a family unit with a son or daughter is positively correlated with assessment of fertility motivations in the individual-economic dimension for wives or husbands respectively.