Being one of four girls, each with our own room, and parents who slept apart, each with their own, even though the house was huge it meant a lack of guest accommodation when we needed friends of any sex to stay the night. My mother couldn't have cared less, she said rather we were somewhere safe and not likely to be done for 'lewd behaviour' in public, and she didn't want young untidy males sprawled all over her sitting room in the morning when she came down. So we took that to mean she wanted them in our rooms, and she quietly bought us all sleeping bags and said that it would be wise of us to use them if our father should investigate. Which he did one morning. It only took him about two years to realise what was going on, he was a bit slow on the uptake, but as we peered at him innocently from our beds with our boyfriends on the other sides of the room in their sleeping bag, we just said it was Mummy's idea. Big row, but somehow she won!
However, when I look back, I wonder why she didn't make us double up and sling the males together.
I just asked the children where they wanted to sleep, and told them to sort out bedding. It was such a minefield when I was growing up, I didn't want that for my children. They appear to have emerged from it unscathed - so far.