Siblings fight for sure ! Personally I wouldn’t be concerned about cross gender sharing. They’re still young and even when they’re older it might go ok. I had my 12 year old son and 13yr old daughter temporary sharing when we had extra kids. They made up their own rules, gave each other privacy and regularly used the bathroom to change.
I would talk about it with your kids and see what they think.

When I was growing up no one bothered about cross gender and sharing. My aunty had six children in a 3 bedroom house and I’m afraid the boy got stuck with the girls. They fought like cat and dog too but I think its like a rite of passage. All siblings fight its just whether or not you can block it out. Sibling rivalry has always been normal behavior. I do believe the 12 year old is entitled to her own room and privacy.

When I was growing up my younger sister annoyed the ……. out of me. My brother ended up sharing with her and I moved into his bedroom. Best thing ever

I would put the girls together. Sisters always fight with each other. It’s a part of growing up! But at 8, I think your daughter would like to have some space without her brother there.

I would be putting the girls back in a room together and it is normal for them to fight like cats and dogs mine do but if some one else makes threats or hurts one the other is right there by their side to protect or comfort. My Grand Daughters aged 12 and 7 do exactly the same thing but the 12 almost 13 year old is always there to mother miss 7. You will catch them having a hug and saying i love you after a fight as Grand Dad and I started this when they were young as we have done this with our own kids.

I would move the girls in together but let them decide between the 2 of them on some room rules.

I would put the girls in with each other, they are getting older now and don’t need boys seeing what they aredoing all of the time, Girls seem to be more modest earlier than boys

My sister and I shared a room until we were quite old and yes, we fought with each other constantly – until we had our own children. Now we couldn’t be closer! My cousins were HORRENDOUS – they’d pull each other’s hair out (but were maids of honours at the other’s wedding). You could try rewards/taking privileges away for their behaviour, but if nothing else works, try to remind yourself that they will probably grow out of it and appreciate each other later in life (and if that doesn’t work – they won’t be there forever!). Good luck!