My FI's cousin got married sometime last year (I think it was about 6 months ago but I honestly can't remember the date). They got married quickly and had a courthouse wedding and only invited a few people (I know my FI's mom went but I don't think the OOT aunts and uncles were invited). The extended family was definitely not invited.
Now my FMIL wants to throw us a joint party. She said like a bridal shower and a "welcome to the family" party for the cousin's wife. We told her we weren't comfortable inviting anyone that we aren't inviting to our wedding, and she said that was fine. But I am kind of uncomfortable with the whole thing. It basically seems like an after wedding shower for his cousin's wife, with almost all people that were not invited to the wedding. But I feel kind of rude saying I don't want this to also be my shower, since the etiquette problems wouldn't be on my side of it. WWYD?