Maybe it's different in the film as the novel also doesn't mention that Michael and Kay had a daughter or that Sonny impregnated Lucy Mancini.
Right, Sonny. Towards the end of the novel, it was mentioned in passing that Kay had another son. I was always intrigued by "what could have been" had Coppola left it like that. Maybe one honest son, one crooked son? It would have been interesting.
