Am I in the right restroom?

So here is my question - how old is too old for a boy to be in the girl's bathroom? I mean I realize when they are really young, if daddy isn't around and you have to go, or the little one has to go, you're going in the girl's room. But what if he's tall enough to reach the sink on his own to wash his hands? What if he's 8? 9?10? or older...isn't it about time for him to potty all on his own?

I'm just asking because the kid I just saw in the restroom with his family had to be atleast 10...weirdest part, his older brother was standing outside the restrooms waiting for them...
Um....????....

It is very hard to have my zen potty break when I am listening to a boy talking in the girl's room...just weird...