It seems as though, through the new movies, the Jedi Council seems to think that there are always two Sith. A master and an apprentice. Are Sith jedi?
If so-- did Ben and Yoda never realize that the Emperor was in fact a dark Jedi? I would assume that at some point in Episode III, the Emperor/Darth Sidious relationship is going to be revealed.
My question arises from the fact that both Yoda and Ben tell Luke- that when Yoda is gone, Luke will be the last of the Jedi. Did they not consider the Sith (Vader and the Emperor) to be Jedi anymore??