My sister's boyfriend moaned my name. What should I do?

Hi everyone, I, 20M, am facing a dilemma. So I've been best friends with this guy since we were 5 and I've been in love with him since I was 16. I never acted on it because he's never expressed interest in men or me and has only ever hooked up and dated women before.

Here's where it gets...messy. 7 months ago he started dating my twin sister who I'm really close to. It was going well between them, and he always treated her well. However, three days ago, she came back crying. When I asked her why, she didn't want to tell me, and she seemed mad at me. I left her to cool down, and eventually, she came into my room to tell me what happened between her and my best friend. So they were out drinking and got really drunk and started making out. Mid makeout session he moaned my name instead of hers. She started accusing me of cheating with him and we got into a really heated fight. Now, she won't talk to me. I've tried contacting my best friend but he isn't responding to any of my texts or calls. I feel really bad because on one hand, I'm in love with him, but on the other hand, I love my sister and I want things to go back to normal between us. What should I do?

tldr : im in love with my sister's bf and he moaned my name and now she won't talk to me