There are some differences in VF2 (as compared to the original VF game) when it comes to producing children. The most significant of those is that couples will be less inclined to have children as family size increases, and arguments will increase accordingly. That doesn't generally prevent a family from having 6 children when both parents have a fairly strong desire for children. However, if you start off with a couple that doesn't have a high desire for children, their reluctance to grow the family will cause a lot of arguments.

Because of this difference, it's more important in VF2 to consider your goals for the family before making your choices for the parents. It's always possible to bypass the parents' wishes and adopt children to achieve the family size you want, but that can be a much more expensive option.