Another little golden moment that just came to mind:

When Michael and Fredo are having their intimate little tete a tete at the café in Havana, Fredo says: "Sometimes I think I shoulda married a woman like you did -- like Kay. Kids -- have a family. For once in my life -- be more like..."

...and we're anticipating that he'll say, "...you." Instead he says "...Pop." Then he sort of reaches for Michael's hand, but withdraws his own. And he says, somewhat angrily, "Why didn't we spend time like this before.?

I guess there's a limit to brotherly love and intimacy when your brother set you up to be machine-gunned at your home.