my brother and I bathed together until we were around 8 and 4 and we only stopped because my brother thought it was funny to pretend he was a water fountain and wee in my mouth. I refused to enter the bathroom if he was in it for years!

I only have 1 child (almost 5) and she now asks for "private space" for going to the toilet, bathing, getting dressed etc. We have no issue with this and give her the space she requests. She closes her door to get changed. Now if I could just get her to stop barging in on me when I'm in the loo! Although we don't prohibit her from entering the bathroom/bedroom if we are showering/changing - we do insist that she knock first though.