have you spoke to him about it?
you've been seeing him for a while, and in the middle of that he's got married to someone else...??
if this is true I think you, and the wife, are better off without him.
i'd tell the wife, then confront him together. and see what he has to say...
(i'm very bitter atm though, and just couldn't stand back and let the twunt get away with it! )