In the novel, Altobello could have suceeded either Tattaglia or Bazini. In the film, he could have succeeded, additionally, Cuneo or Stracci. During the war in the 40s he could have been a capo, underboss, or consigliere of any of the other families.

The only relationship between he and the Corelones that we can be sure of is that he was the Corleones oldest friend. Profaci was a friend to the Bonannos. So, there is precedent for such a relationship families.