The aim of this paper is to develop a model which incorporates the elements that are crucial for the determination of population dynamics in poor countries – child labor and intergenerational flows from children to parents. This model shows that when income decreases, fertility rates increase; a correlation which cannot be obtained by the regular models of demographic transition, in which there is a positive correlation between income and fertility rates. The main advantage of this model is that it better fits the data and the socioeconomic context of the poor countries. The parent-children relationship is part of a whole set of values and social norms that evolve over time and are affected by changes in the economic environment. Intergenerational transfers from parents to children are not due to an intrinsic value, which is independent and invariant to economic changes.