Just think how could it be if Appolonia have had a the baby before the car bomb. and for say think michael and vito had have the baby boy hidden in sicley for a long while. As he grew he get's involved in mafia. This just what Micheal wanted, this could be his secrect weapon. Please add to this.

Sonnyboy, is your real name Mark by any chance?

Yeah sure. I can see the whole thing. Apollonia's family is hiding the kid, mafiosi are shouting about how anyone who hides him will be punished, so they hide him in a donkey and send him to the US where he secretly lives with Lucy Mancini and her son, where they develop a Michael Corleone/ Tom Hagen love-hate relationship. Then again....