The 4th being Naruto's father kind of would make since with all the likenesses there are, who knows? It make him an orphan if he wasn't one before that. I know the rasengan isn't some blood trait but theres only 3 people to my knowledge who can do it which is of coincidence if you ask me, but the 3rd holding the child is probably just the purpose of moving the story along. Probably just purely conicendental in my opinion, but an arch on the caretaker and his parents would be interesting would it not?