Originally Posted by Aurora

With cats they can be only half siblings. Every kitten can have a different father.

I once had a male cat that took his turn sitting with the kittens. While she was giving birth, he never left her side and would lick her on the head when she cried out in pain during delivery. That night she took the babies one at a time and put them with the father in his favorite sleeping chair and he was still with them in the morning. From that point on he took turns watching the kittens.