Inspiration for THE GODFATHER?

First, watch the film:



http://www.youtube.com/watch?v=6kHrPl2TNao&feature=youtu.be

Now...

Both films have:

A strong Italian immigrant father with four sons (I'm counting Tom Hagen)

An older son bitter over being ignored for the younger favorite (GFII).

A weak-willed son

A slow-thinking son

A son who is a shady, streetsmart lawyer.

In the original script of Godfather II, Tom has an affair with Sonny's
widow, and here Tony marries Max's former fiancee Maria

Both films even have a scene where the father holds up a family
get-together while they wait for the arrival of the favorite son.

I am willing to bet Puzo read Weidman's novel or saw the film -- probably both.