Ha. My parents are totally weird about this.
We moved in the late 80s, & dB & I fought tooth & claw for the lovely big attic bedroom. I won, because I was a couple of years older & it was agreed he'd get it when I went off to uni 3 years later.
He barely managed to wave me off - he was too busy painting his new room black & hanging his Warhammer & Iron Maiden posters
. Fair enough!
He then remained in there for over a decade until my dps finally changed the locks persuaded him to move into a flat share. Dps, with indecent haste, sold up & retired to a smaller place in the countryside before dB could change his mind...
Fast forward 20 years & I'm divorced, living overseas, & when I do visit the U.K. it's for a couple of weeks - I spend a bit of it with dps but travel a lot to catch up with friends, & always insist I could get an Airbnb anyway (they won't hear of this).
So after a year of this I returned for a visit to discover that dps had...taken their nicer spare room, dug out a box of my teenage crap from the attic & basically recreated my teenage bedroom! My A level textbooks are on a bookshelf. My teddy is on the bed. My framed Maggie & Ron Gone With The Wind CND poster is on the wall.
I'm nearly 50
.
Db is 
because now when he visits them with his dw & the dns they're all squished into the inferior spare room or on blow up beds in the dining room!
I've said there's no need for this but it's fallen on deaf ears. 'No no Purple! That is your bedroom now!'