I was watching the Godfather II on DVD, and I happened to pause it perfect in the senate hearing scene, right where it shows the family tree. I looked real hard, and I saw that Fredo Corleone was listed as the underboss. I thought he was small potatoes!

Although I am asking others for their opinion, I think I could give one of my own. Fredo Corleone was given a title to keep him happy, while Tessio in GF1 and Lampone in GF2 really was the underboss. Fredo was happy with his title until he figured out that he really didn't have much of a role in the family position at all.
~Sal