If the old man is Nazorine's father - certainly a possibility, but something we can never know for sure one way or the other - then what was he doing at the meeting of the Dons also?

If he was a Don himself (perhaps the un-named head of the missing 6th family?), then there's no way he could have also been Nazorine's father. If he were a Don, why would Nazorine have to go to Don Corleone for assistance.

So on that basis, if he was Nazorine's father, what was he doing at the meeting?