Recently I went on a trip with my partner and three other couples, including my sister and brother-in-law. One afternoon everyone went into their respective rooms for some downtime and my partner and I debated fooling around. Then we overheard my brother-in-law in the living room say to my sister, “I’m gonna go listen to them have sex!” We heard him attempt to tiptoe over quietly where he stood outside of our door for 10 or 15 minutes. My sister did tell him to leave us alone, but she went to her room shortly thereafter. I’ve never liked my brother-in-law and now I’m humiliated, disgusted, and don’t want to spend time with him ever again. Do I say something to my sister? This isn’t the first time he’s been inappropriate; last summer he seriously suggested wife swapping. He and my sister fight incessantly and he has no respect for her, so I don’t know if she would even say anything to him, or if anything would change if he did. I think if she did talk to him, he would still blame it on me. How can I prevent this from happening again? How can I prevent this from hurting my relationship with my sister?