When I was married and there was family drama that included me, my EX H's family did the same thing. I would send a letter to each one of them that's worded something to this effect:

Dear _____________:

I understand you are upset with me about _____________. While I can't change your feelings, I can say that your continued efforts to prolong this issue is tearing our family apart. I am extending the olive branch to forgive and forget, live and let live. The last explanation I will give is ________________________. From this point on, I do not want to hear any more about it, from you or others. Moving on is the way to healing and having a family. If you do not want us as part of your family, please tell us now so we can move on and heal. If this is not the case, then get over your hurt by telling me one last time what I have done to you that was so egregious. After this, you must let it go. If you can't, then we are obviously acquaintances and not family.

Much Love,

_________________________

I sent out at least 5 of those because they didn't like me, flat out. I was more educated than they are and they were offended by my "big words". They also took my allergy to coconut and sugar and gluten sensitivity to me being rude by not eating their food. Each holiday or get together, I would have to send these out.

There were a few that said we are not family, and that was fine by us. One less person to worry about.

Eventually, we divorced, but his family still respected me and didn't breathe a negative word in my direction. (The issue for divorce is unrelated to this letter, btw. )