I believe trilogies become successful by using references from the previous movies. The Godfather III had a good reference by relating the character Vincent Mancini (the Illegitimate son of Sonny Corleone, for all of you who dont know) to his father. But as for the part of George Hamilton they should have elaborated more on his part and explained where he came from. He had been a long time since the second one so I would understand why they didnt.