It been said that the sons represent the parts of human nature: Sonny is ruled by emotion or passion, Michael by intellect, and Fredo by the physical. I think that's why Puzo threw the cooking thing in there, to show that's Fredo's key is the satisfaction of his physical needs.
Pete, years ago in another Forum I opined that none of Vito's kids inherited all of Vito's characteristics. We know that Vito was capable of violence, that he could be sensitive, and that he was quite intelligent. You can argue that Sonny inherited his violence, Fredo his sensitivity, and Michael his intelligence. Of course, the novel explains exceptions to the foregoing; even the films illustrate some exceptions.
