Attire for guest at wedding after party...

So you're b-listed to an afterparty on your own dime? I'd wear whatever is comfortable.

For lurkers, that's a really rude way to treat the people in your life.

Echoing off of the b-list thing, I'd probably wear a nice blouse and dark jeans, which is what I would wear to any party that occurred at a bar. I wouldn't dress up for a wedding that I wasn't invited to that had already occurred.

Wear a business casual type dress or a cocktail dress to the reception. So you are b listed to an event that you have to pay for your own meal and drinks and there is another wedding next year? Are you expected to bring a gift to both as well?

I would not go to the reception, you are nicer than me!!

Good gosh - I missed the part of a small courthouse ceremony followed by a small reception THEN we are invited to a bar for an "after party" where you pay for your own food and drinks. So let me guess - he is calling both events a wedding and maybe wants gifts for both? The first event is the wedding, the shindig next year is a vow renewal/celebration of marriage and you should decline everything. The fact that you stated the guest list has been touchy leads me to believe there is some drama/tension around this whole thing. Stay home and watch Dateline or go out with your friends. And I would not invite this cousin to my wedding.

I'd personally be wearing my jammies, since I wouldn't be going. But for something like that I'd echo a dress or nice jeans/pants and blouse.

It might not be the best etiquette for cousin to do, but the OP might have good reasons to go. Keeping peace in the family, for example. Sounds like the way cousin is doing it has caused some hard feelings and stress for everyone.

I'd wear a casual skirt or dress.

I hear you MOB but it is not the OP's job/duty/responsibility to keep the peace.

Stay home OP.

This is the kind of thing people who plan to do this are convinced won't happen in their family and their guests totally understand that weddings are expensive etc etc etc. Thanks for sharing it's caused some strife in your family so people can see that hurt feelings actually do happen!