Thanks for your answers - both are great. Particularly valid is the point you make about Tessio's treachery being aimed towards Micheal and not Vito, a problem for The Family which perhaps first reared its head at the meeting between Micheal, Vito, Tom, Carlo, Clemenza and Tessio. During this meeting, Tessio and Clemenza both approach Vito for permission to start thier own family's despite Micheal being the new head of the family and the one who would make such a decision.

However, one issue I have with your assertion that Tessio was 'as loyal to Vito as Clemenza was' : Tessio's treachery was in full effect by the time of Vito's funeral - does that in some way counter that notion?