Annsixty, I'm with you. One of mine age 17 asked if she and boyfriend of 18 months could share her bed when he was staying here after a night out, I'd encouraged her to talk to me when contraception was needed, she did and saw our GP with my full support as aged over 16 by then. I refused to let them share a bed in our home because I said it would set a precedent for the next bofriend, the one after that. Also, they had any number of opportunities to be alone in our home, or boyfriends parents home, so no need for the back if some bushes in the park.
By second year at university, they brought home steady boyfriends and shared a room. I still feel 16 is young, not to be having a sexual relationship but to be insisting on putting the rest of the family out to prove a point.