This argument assumes the older children share the parents' goals. If the children are assumed to possess free will, it is possible that the older ones' action

This argument assumes the older children share the parents' goals. If the children are assumed to possess free will, it is possible that the older ones' actions could result in an increase in the amount of work for the parent as they got older. It is also possible to "raise" children one did not have biologically, and to have more than one child at a time biologically. Twelve children born together would be... tough. For a number of reasons.