My older brother recently kicked his wife out of his house, and his new girlfriend has moved in with him. Before this all happened, my brother came to me and told me what he was planning. It was really hard for me to do (because I've never in my life told my older brother what to do), but I told him to cut off his affair, get back in good with the Church (he hasn't been practicing in a long time), and to get his marriage into counseling. This had no effect. Since then, my wife and I have been on our own in opposition to my brother's choices. My parents never got along well with my brother's wife, and so they've basically been consenting to all of this. The day after my mother found out, she was investigating getting him an annulment (as if he even remotely cared about his standing in the Church).
Everyone else in my brother's life has met his new girlfriend, and everyone treats this as though there is nothing at all wrong with it - it's just the new normal. They go out to dinner with my parents, she joined his softball team, everyone is friends with her on facebook, etc. My brother hasn't tried to introduce us yet, but he's gotten clothing gifts for my kids which I know were made by her.
What am I supposed to do? Am I supposed to be civil to her? Am I just supposed to be ok with taking my kids to family Christmas with her there? I've read a lot on these forums about people contemplating attending weddings for couples like this, but I'm nowhere near that point.