poor beom and his internalized homophobia. he always thought even the slightest kind gestures like getting his brother gifts or standing less than a foot away from him under any circumstance was “too gay.” when kai banished gyu to his room and told him to blast a show or some music, gyu couldn't help but imagine what it would look like for his brother to lose his virginity. but he didn’t need to keep to his imagination since he collected enough audio data to understand how his little brother is in bed. now he knows why kai told him to blast something instead of just wearing his headphones casually. because he is Loud.
at first, beomgyu just starts laughing to himself at how much of a whore his little brother became for dick. like damn is it really that good? beomgyu caught a glimpse of kai’s little boyfriend or hookup or whatever when kai was rushing to get him in his room. he can’t lie, the guy didn’t seem like he was packing much, but it sure sounds like he knows how to use it. he would’ve been more intrigued if he heard some slapping or spanking noises, but he assumes they’re keeping it vanilla for kai’s first time.
the more beomgyu diverts his attention to the boys next door, the more his hand finds its way down his pants. fucking creep. if he closes his eyes, it makes him feel like he’s watching porn, but in real life this time. so he does just that. he pulls his sweats down to the middle of his thighs, grabbing his dick out from the side of his boxers since he’s too lazy to fully undress. “taehyun, shit. oh my god…” “you’re doing so good kai. keep going for me.” beomgyu overhears their intimate exchanges and that only fuels his fire even more. he can’t believe his dick is wet because of the sex his little brother is having, but he can’t find any sort of guilt within him.
he moves his hand faster and faster as kai gets closer and closer to his climax. he times his strokes with the pace that kai’s bed creaks against the wall, which is surprisingly quite fast; beomgyu didn't know thrusts could be this fast before. and he cums nearly seconds after he hears his poor little brother getting the best orgasm of his life (so far, at least). wow, he's sucrech a pervert.
a few days later, beomgyu would casually ask kai over dinner, “hey kai, if you wanted to have a threesome, would you have it with someone you know or don't know?”

writing this made me think about this tejun fic (milf jun, alpha tyun) for some reason shoutout to rua (soobducted) for this masterpiece!!!
https://archiveofourown.org/works/59927275