Opinion

Eh, I think it depends on your having dynamic and culture..

When we had sleepovers with cousins of opposite genders we all slept out in the living room with our own blankets because frankly, even girls can molest each other.

I never had any issues at mixed gender sleepovers with family but I was groped by 'friends' sharing a bed multiple times past the age of 8, and that was hell to work through.

Why not suggest an open area for them to sleep in? Or just gracefully bow out at 10 or so, where they can stay up late and do whatever but they go back home to sleep. I wouldn't have an opposite gender sleepover in the same room together, and have never thought to host any since we have kids so far apart in age anyway in our family. You are your child's strongest advocate. If you don't feel comfortable with that for your child, that is fine, full stop. You don't need to justify that decision to anyone. Keep your child safe and do what works best for your family and keep your peace.

I think 3 people sharing one bed is a little much but I also agree the boy should be sleeping separately. I would suggest the kids share an open space together.

I wouldn’t mind as long as the kids were comfortable with the situation. Personally, I always made sure my niece had her own space, but her & my son always ended up falling asleep watching movies in the same bed/couch & at my parents house they always chose to sleep in the same bed bc otherwise it was different rooms & they weren’t as comfortable away from their own spaces alone. They’re 4m apart, supposed to be 2 months apart but niece came 2 months early, but at 10 they kinda started drifting apart, the last time they slept in the same bed they were 9 & it was Easter eve, they’re 16 now & prob wouldn’t, but we still wouldn’t say anything if they conked out in the same place,but we now KNOW for certain they wouldn’t be doing anything, even if they are actually step cousins, but like little bro & I, they don’t see each other as step, they both put some old dude in his place w/ eww-ing & choice language, when he grossly suggested they might grow up & get married bc they were so close. 🤢