Poor families have more children and transfer less resources to them. This suggests that family decisions about fertility and transfers dampen intergenerational mobility. To evaluate the quantitative importance of this mechanism, we extend the standard heterogeneous agent life cycle model with earnings risk and credit constraints to allow for endogenous fertility, family transfers, and education. The model, estimated to the US in the 2000s, implies that a counterfactual flat income-fertility profile would-through the equalization of initial conditions-increase intergenerational mobility by 6%. The impact of a counterfactual constant transfer per child is twice as large.