I got called insecure for not wanting to do a 3some with my husband and his sister.

My husband proposed the idea of a 3some with me and his sister. He called me insecure and rude for not being okay with the idea of it. He says that he doesn’t want her to feel uncomfortable because I won’t let her kiss me and that it would be good for our marriage. I’ve been arguing with him for a week over his refusal to listen to me. My husband has always been a very caring and loving person, but him talking about this makes it feel like he’s emotionally cheating.<br><br>What should I do?<br><br>EDIT 2: I can’t respond to every comment but I’d like to say that I have never seen or spoken to his sister. I also don’t know why he wants this so badly. I feel the need to speak to his family so I will update once I have.