Our RSVPs are due in a few days and we're getting some flack from one of my FH's aunts.
It all boils down to family drama, but a little back story...Aunt and Uncle have been married over 30 years. Aunt is FMIL's sister and Uncle is FFIL's best friend since they were kids. Aunt walked out on Uncle about 3 years ago. Neither has filed for divorce, they're not even legally separated. Aunt moved out of marital home and into her boyfriend's home. Since then this entire situation has divided FH's family on choosing Aunt or Uncle's side and Aunt has been doing some pretty nasty things to Uncle just to hurt him including leaving him financially destitute and manipulating his kids against him. FH and I have never met the boyfriend and really haven't seen Aunt
more than once in the past 3 years. We see Uncle pretty regularly since
he is still friends with FFIL.
When we sent invitations we invited both Aunt and Uncle as singles. While I know that people in long-term relationships should be extended a +1, I didn't think it was appropriate to invite Aunt's boyfriend while she's still legally married to her husband who will also be at the wedding. If they were divorced or had at least filed I might have felt differently since they were taking steps to dissolve their marriage and move on, but for this Catholic family it just seems like she's rubbing this relationship in Uncle's face and openly committing adultery. At this point I don't want her at the wedding and FH has said she's no longer welcome in our home or at our wedding because of how she's acting and being nasty to FMIL.
So, should I apologize for not inviting the boyfriend or is this a case where etiquette doesn't apply to rude and nasty people?