If there is enough space, everyone gets their own room. If not, then not.
It’s not an existential problem, in my opinion even a luxury problem.
The three of us sisters shared a 15sqm room until the first one moved out (at 23).
Sure, it was cramped at times, but it couldn’t be helped and it never even occurred to us to complain about it.
Honestly, I’ve never heard of anyone else feeling unhappy because of that or anything like that. It just wasn’t questioned because those were the circumstances.
If I had several children, whether each had their own room would be my least concern.
We had the best years of our lives when we all still shared our rooms. And sometimes there were 2 friends staying overnight at the same time and it always worked out.
Wonderful times, when parents didn’t interfere in every little thing their children did and you could simply be a child without issues of recognition.