Originally posted by AppleOnYa:
If Sonny remained alive then there would've been NO GFII, because he would've run the Corleone Family into the ground before Michael ever had the chance to touch it.
One of the main underlying themes of The Godfather was that Sonny, the eldest son and heir apparent, HAD to die so that the Family would ultimately end up under the guidance of the youngest and least likely son.
Apple
I disagree. If that's the case, then Fredo Corleone would have become Boss of the Corleone Family after Vito Corleone had died.