and to all those who think that just 'cause a guy took care of the kids once he always should imagine this scenario:

The girl gets pregnant from one guy while married to another, then divorces, remaries, the new husband takes care of the kids, gets divorced remaries the new husband takes care of the kid: so now she has 3 guys paying child support??

Emanual Kant argued that maxims which cannot be universaly applied should be morally forbidden. The idea that anyone who assumes a "fatherly role" must pay does not pass this sort of test.