BTW, in a deleted scene, Neri shows Michael a photo of Fabrizzio, and tells him that Fab entered the US in 1955, "sponsored by the Barzini family." That tells me there was one or more survivor(s) in the Barzini family with a link to the past, even if it was to make good on a promise Barz made to Fab.
This is why the saga is so much beter, i wish thy would show it every other time they plan on showing just the regular movie on tv.
