Somewhere around 20 years old, my parents stopped caring. Before that, boyfriend-of-the-week and I weren't allowed to stay in the same room... but once I hit 20 or so and had a v. serious boyfriend, they became okay with it. Heck, they were the ones who suggested we move in together.

many years later now, I live with my fiance, and parents, grandparents, etc. don't have any problem with us sleeping in the same room... we do the other 364 days of the year.