This is more my curiosity than an "issue."
My stepdaughter (22) goes for an overnight visit with her mom and brother (20). Currently there are only two places for guests to sleep, the living room sofa or the top bunk of her brother's bed. She has normally crashed in the top bunk of his bed, mostly because the two of them sit up half the night playing video games.
Mother's boyfriend is freaked out about her staying in her brother's room, he thinks they'll get up to (or are engaging in) pervy stuff. Her mother even thinks the BF is over reacting, but she completely defers to him about everything.
Now up until the kids said ENOUGH we went on camping vacations. Sleeping in the same room with your siblings (heck, even in the same bed, two kids fit with plenty of room to spare on a king sized bed) isn't something that seems odd to us. The kids "pajamas" are basically comfy street clothes and any clothes changing takes place in the bathroom.
So, adult brother and sister sleeping in the same room, NOT in the same bed, creepy or normal?
For the record, my stepdaughter, her father and I think the fact the BF's mind even went there is friggin' creepy.