We enter this world helpless. Our parents owe a debt to us when we are born. They have obligations to us. Every society operates in terms of this principle. Parents who refuse to care for their children are placed under social sanctions. They are encouraged to provide care for their children: positive sanctions. If they refuse, they are punished in one way or another: negative sanctions.
Humans are slow learners. It takes longer for humans to reach maturity as a percentage of their lifetimes than any other species. So, parenthood is a long-term commitment.
Prior to the longer lifespans produced under capitalism, one or more parents died of old age before all of their children reached maturity. Other family members would then step in and care for younger children, usually older siblings. Again, this was a debt relationship.
