My husband's sister has two kids the exact same age as my kids, but opposite genders.
They live about two and a half hours away so we see them regularly but not that often. Usually during the Easter, Summer and Christmas Holidays, so about 3 times a year. They stay in MIL's holiday caravan in a nearby site.
The kids and adults all get on great.
This year, DH suggested to them that the kids have a sleepover at ours while they are here, which would be fun for the kids and would give them a night to go out. This was enthusiastically accepted by kids and adults. He has said they can either sleep indoors, sharing bedrooms with our kids or camp in the garden in tents if it stays nice.
I'm very happy with this accept the thing is, DH thinks it would be fine for the two 13 year olds, of opposite genders, to share a bedroom or tent. I'm really uncomfortable with this and think it's a bad idea. I've suggested that the two younger ones share and the older two sleep apart, maybe one on the sofa or something.
DH thinks I'm being weird and paranoid and that they're cousins so it's fine, and I'd be spoiling their fun, but I just think it's inappropriate.
DH says he doesn't know how he's supposed to suggest this to his sister and BIL.
AIBU?