When I was a child (60 years ago) the neighbor family had 7 kids in a 2-bedroom house. The three girls got one bedroom; three boys got the living-room (couches and mats and sleeping bags) and the parents plus the baby got the second bedroom.
I actually never thought twice about it, until now.
I do know that "the family bed" is much more common in some other countries, for instance where houses are much smaller, families are much bigger, and one-bed-per-person is practically unheard-of.
So I'll hold off on my judgments until I know more about it.
Family bed doesn’t go up to age 20. Family bed is awesome for little children. Everyone sleeps all night long. No scared waking in the night because they know you are right there. However, for the sake of the marriage, the family bed needs to be in the child’s room. Master bed needs to be No Children Allowed. Adults need a place to be alone. Adults with small children don’t need to actually SLEEP with their spouses. Little children NEED their parent in the night. For security and not just emotional: no kid sleeping with their parent will be kidnapped.
Mom and Dad had their own bedroom ... and heaven forbid if any of us entered that room uninvited.
I and the second-oldest brother shared another bedroom on a bunkbed; I had the top bunk because I didn't want to run the risk of him stepping on me in the middle of the night if he had to go to the bathroom.
The three youngest brothers were in the last bedroom, on a three-tier bunkbed.
It was like that until I reached 18 and left for the Naval Academy. Then the middle brother moved in with #2 brother, making it two-and-two. And so it was as one son after another left home.
I'm not talking about multi-person bedrooms. The idea of a grown .. or even teen .. child sleeping with their parents takes a special kind of snowflake. Or helicopter parents equipped with a heavy-duty electromagnet. Or both.