If Fredo had not been killed, what do you think Anthony would have grown to be? It seems from GFIII that he didnt want to get mixed up in Michael's business because Fredo was killed by Michael. But, assuming that Fredo wasnt killed by Anthony's father, do you think maybe Anthony would have partaken in the family business?
I think there really isnt a clue as to what he might do in such a case. However, maybe Kay would have forbade him from it....