The "regular" bath layout that jensbride posted first is very similar to what our DD & DS shared for years and worked very well. The door, however, was a pocket style and placed directly across from the toilet. This allowed the vanity to be scooted around the corner to take up the whole wall. It leaves the toilet close to the tub, but with lots of elbow room. Our kids just learned to keep the door partially closed when the bath wasn't in use due to the "view".

Thanks for the ideas mayflowers. I definitely realize that 9" drawers are small! Believe it or not we have 6" and 9" drawers in our master bathroom right now, not by choice, and my 9" drawers feel very roomy compared to the 6" drawers my husband is stuck using. I figured the 9" drawers would be able to hold some of the basics like toothbrush, toothpaste, and a few odds and ends. Right now all of those types of things are stored in the cabinet over the toilet, which doesn't seem like the best scenario for every day use. I will definitely reach out though to find out the exact inside dimensions of the Barker doors. I also realize that 30" drawers are huge. I was just looking for a way to fill out the rest of that wall. The wall where the pedestal sink is now is only 21" deep total on the tub wall and is only 18.5" deep from the corner to where the tile starts. I was thinking that I couldn't do an 18" deep vanity there. With the 1.5" countertop overhang added on to that would push it into the tile. I do like the idea of centering the sink but was just concerned about it feeling cramped. I wonder if I centered the sink and then bumped the vanity back to 15" deep on either side might work out well. I do think that the scones through the mirror sound lovely. If you did a 36" vanity, would you use a 24" sink base and a 12" drawer?

It looks like it was added at some point. And it extends into a space behind it. What do you want to store? I’d think another built-in with drawers below and a cabinet with shelves above would provide good storage for bathroom items.

If they would each be the size of the standard 5x7 bath that used to serve as the only full bath in the house, and it has no negative affect on your budget to have another or negative effect on the bedroom size it would be fine to have two individual baths. If they would end up being cramped or shrinking the bedroom, maybe not. It's not so much that smaller bathrooms are that much more difficult to use, it's that they are a pain to clean. You could also do one ensuite and one hall access...and by the time the older one leaves the younger could move into that bedroom. I would not do a single Jack and Jill or the two sink thing. There are differing parenting styles too, and I know some parents more or less stay out of their teenage kids rooms, so it's possible that ensuite bathrooms in that situation would get really dirty. I once stayed overnight in a guest room last minute that was jack and jill with a kid's bedroom, (kid home) and they had me use the ensuite bathroom in a different kid's bedroom who was gone over that night or two. And the ensuite bathroom was not exactly filthy, but it was not clean or taken care of by a long shot. And they didn't know because they stayed out of their kid's rooms.