[fun4dandj]

It seems like you should follow the first rule of swinging, be honest. Tell the couple that you found them to be incredibly cool at the meet and greet. Then explain that you heard that there was an episode where he had attempted to perform oral sex on a straight guy when the guy in question hadn't agreed to that in advance. See if its true and he's bi. Let them know that it is unacceptable at your straight male party, and that they will have to either not come or don't behave that way.

My husband is bioral for lack of a better label. He would never in a million years consider doing that to some unsuspecting straight guy. In our opinion and in the opinion of many of our friends, both straight and bi, you descide on the boundaries ahead of time and play within those boundarys