The long and short of it is that I would go. You have accepted him as he is or you would not have invited him to your wedding, knowing he had a male partner. He would probably not fault you if you declined for whatever reason but it would be hard for you to live with that decision. While this has been an interesting thread it is incomplete without knowing how you arrived at your decision to go and what is your wifes take on all this?
He knows how I view gay marriage....and I am sure that he knows that I am not there to show any support for a gay marriage movement - he knows I will be there because he is my cousin. This reason is enough.
.My wife says that a Marriage should be between a man and woman --- and we pretty much agree that there is a place for civil unions. We're going together