Four kids, 2½ bedrooms.
I shared with one of my brothers until the age of 14. Then I got my own room - it was a box room, but the younger two had been sharing it until then. The younger three then shared the proper bedroom, with a partition so my next-oldest brother could have his own space; also very small.
When I started going out a lot, so maybe around 16, Dad converted the old coal shed into 'my room'. It sounds downright abusive to modern ears, but we all thought it was pretty cool and the others couldn't wait until I left! Brother then got the 'shed' until he left home - with him outside, the two youngest could each have a room. Mum commandeered half of the partitioned bedroom for her craft stuff.
I've never thought about a connection before, but I only have a completely easy relationship with my next brother - you know, where it feels like you've just picked up from your last conversation , even if it was months ago? I wonder if it's because we literally grew up together, in the same space?
I had lots of friends who shared four to a room, and have also known several families that had some sort of rota system for the bed in the kitchen and/or on the sofa. Children actually like being physically close, remember, and the middle-of-the-night conversations feel hugely important at the time.
Tbh, most kids would be happy with a tent out the back, as long as they could get to the loo and the kitchen.