Godfather part 3 question

[Nick419]

i'm a fan of the godfather series and always had one question that stuck me................why the fuck do they have vincent and Michael's daughter fall in love? I mean there cuzins for gods sake and through out that movie it just grossed the shit out of me when they had love scenes,etc.i dont really care i just found it weird they'd do that when the godfather series are hugley popular and some people would find that disturbing lmao