Boyfriend's brother kissed me when I was drunk and I'm conflicted on whether or not I should mention it to my boyfriend. Thoughts?

Apologies in advance but I just want to be thorough here.

My (22f) boyfriend's brother (22m) just came home from military leave after three years and is staying with my boyfriend (24m) until he gets back on his feet. I only first really met him when he moved in like 2/3 weeks ago, and we seemed to get on pretty well. Last night, all three of us went out for dinner and a few drinks, then continued drinking when we got back to their place. Now I'm still pretty new to drinking and have issues with pacing and portion control, while they've both been drinking since they were like 14-16. Needless to say, I was essentially wasted while they were barely tipsy.

The last thing I remembered before this happened was that we were all watching a movie and then when I came to, someone was kissing me. I thought it was my boyfriend but then when I managed to open my eyes, I saw that it was his brother and immediately stopped and tried pushing him off of me. He didn't budge though and said something along the lines of me "begging for it all night" and kept touching me and trying to kiss me. I was abused as a kid and ig this kinda brought me back, so at that point I just sort of shut down and froze.

At some point, their other roommate started coming down the stairs and that's when he finally got off of me, telling me not to say shit to anyone. Ig I was in shock or something cause I didn't know what to do. My boyfriend had apparently gone outside to smoke and when he came back, he noticed that I was looking a bit out of it and took me upstairs to go to bed. That's the last thing I remember.

This morning, my boyfriend asked if I was feeling okay and I just told him that I thought that I drank too much last night. His brother was still sleeping when we left.

I'm just a little conflicted on whether or not I should mention what happened to my boyfriend. Him and his brother have a somewhat rocky relationship, with the former having to essentially parent him when they were kids
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due to an absent dad and a drug-addicted, negligent mom. He still sometimes does this, and his brother still seems to act like a teenager in a lot of ways, so it can be a bit messy. They've seemed to be getting on well so far though, and I don't want to ruin it.

Maybe I did unintentionally lead him on too, I'm not sure. I didn't mean to if I did, I was just trying to be friendly.

*Continued in comments*
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I don't think he did anything beyond groping and kissing me either, so while I'm obviously not happy it happened, I don't think it was anything too serious.

I don't know, I'm just feeling really torn. On one hand I feel like a piece of shit and like it was my fault, but on the other, I don't want to ruin what seems to be a decent situation for them.
Boyfriend's brother kissed me when I was drunk and I'm conflicted on whether or not I should mention it to my boyfriend. Thoughts?
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