And when they’re young, a boy and girl in the same room is absolutely fine.

This. 3 kids here in a 3 bedroom house (~1100sqft). One in high school, middle, and elementary. It works, although another 500sqft would give us some more breathing room.

Since my boys are teenagers now, I spent the pandemic building a rather nice lofted bed setup out of baltic birch ply for their shared room. It gives them their own personal space (had them help design use cases) and more privacy than most kids in the world have. One is autistic and hypersensitive to the others habits, but I was able to mitigate 95% of that with visual blocking, acoustic materials, and a HomePod mini for pink noise.

You make do with what you have. Some of son’s friends live in 5-10M houses, some live in trailers, some in apartments. I think they all understand that, while they probably want more, they’re lucky to have this.

I am more than comfortable for that to be your 'dream home' but it is not my dream home.

Seeing a lot of this in private school.