It would be disingenuous -- if not downright catty -- to inquire about B's wife in front of C, or to start inviting the wife out socially. O.P. stated that she had only met the wife once in four years.
I didn't catch that but you're absolutely right. Whole new spin. OP, if you've only met the wife once in four years, how do you know they didn't separate a long time ago?
OP also states how it's 'icky' because he's still married. That's a personal judgement. Many people start seeing other people while separated and long before a divorce is final because these things take a long time. There's absolutely nothing wrong with that.
I think judgements are being made about peoples' relationship status that shouldn't be being made (terrible English, it's early here!) and I stand by my original statement that it would be terribly rude to big up the wife in front of C, *especially* considering that the OP doesn't even know her.
Yes, sorry, I had already discarded any idea of bringing up the wife, or inviting her for exactly the reasons stated.
As to being judgey: If they are separated, they should...separate. Not live in the same house with one another. Not be underhanded and shady with your new relationship
. <NEW INFO> Not suddenly start to wear your wedding ring because people were "getting the wrong idea". If they are separated, why not tell your friends who are observing "bad" behavior and clear it all up? Honestly, we don't hold divorce against our friends (Actually, now that I think about it, one of the guys in the group did separate and eventually divorce, and started seeing someone who was welcomed into the group before it was all finalized). If that's what's going on, he should just say, "Wife and I are separated, and I'm seeing C now." As I said before, it's the one foot in, one foot out that I find the most distasteful.
Regardless of their circumstances, real or imagined, without a clear declaration of his attachment, B and C are not a social unit and are not to be afforded the privileges that come with that, such as joint invitations.