As I've stated on this topic before, I think Puzo had a strategy when describing the siblings characteristics. That strategy was to provide contrast between them and with their father. Several of you have described those characteristics. Check them out again. They are all characteristics of the Don.
Like Sonny, he could rage and kill. His rage was internalized though; his demeanor was pacific most of the time.
Like Mike he was intellectual,cunning, patient, and persuasive. He knew when to compromise and when to wait for a better opportunity.
Like Fredo he was sentimental. He truly loved his family.
Like Connie and Tom? I'm not sure. Perhaps he was conflicted - feeling forced to do what was not in his nature, but which he felt circumstances forced upon him.
The kids were bits and pieces of the Don interacting with each other.
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