I used to share a room with my younger sister until I was 14. It got to the point where we hated each other and our sisterly bond was pretty much non-existent. Then my oldest sister moved out and I moved into her room and suddenly everything between me and my youngest sister was cool again. We weren't at each others throats every night and we became really close again.
Now I share a place with my other half and I have a little desk area that's exclusively mine even though we share all of our space. I think it's important to feel you have control over your own space, even if it's just a little corner