Here is how the window-seat area in the girl's room looks like right now.
Sky built-in bookcases on each side of the window seat area, and built the window-seat out, making it wider and more comfortable to sit on.
We need to find a cushion for the seat.
Oliver finds it plenty comfortable, it seems.
Here is the best "before" photo I could find.
This is the room before the great "sleeping-loft" project began...notice no bookshelves flanking the window, and the seat is not very deep.