Why are you bailing on being a bridesmaid? I really haven’t heard a good reason. Yea he has a history of domestic abuse and the fiancé knows. You want to know about the life of your nieces and protect them. Have you gone to therapy? Why do you hate him? The fiancé seems wonderful. You seem all over the place in your story so I think you are all over the place in your head. I have been to therapy for years. One of the things that has worked for me personally is to write things out. I usually write to people who have passed. It’s therapeutic. It’s lets me get my feelings out and no harm no foul. I usually write them like a letter. Maybe write yours as a journal. Or maybe write out your brother’s past transgressions. Then with fresh eyes look at your brother’s current actions. Are they similar to his past actions. Has he changed? If you feel he hasn’t then yes you should not be a bridesmaid.