[smut question 18+] asexual writer here—moral implications of a threesome with two brothers?

I'm likely overthinking this, but as an ace dude, I have no idea. I wrote a cute romantic-only oneshot about a love triangle between a character and two men (brothers to each other) and they decide to "share" their partner at the end. I've received quite a bit of positive feedback, with many people asking for a smutty part 2 (I have written smut many a time before, and am comfortable doing so). Yet I found this peculiar. Surely that crosses an incest line? I'm not certain if this is a real thing people do in real life, or if my readers want to suspend their disbelief for the sake of fiction (à la "non-con" readers who oppose such things irl). Allosexuals, I beg for thine assistance!