Yeah, my mom is one of 6 and they lived in a house with 2 tiny bedrooms and one bathroom. The larger of the two bedrooms could fit a queen bed and a dresser with only enough room to crawl into the bed from the foot.
Of course, the oldest was 18 when the youngest was born, so I’m not sure there was a time when they were all there at the same time. And they had a walk-in attic and a basement that they were able to convert into bedroom space. Otherwise, I’m not sure how they could have managed.
I knew a girl who was one of 11 and they had a 3 bedroom, 1 bathroom house. As with many of the above replies, it was divided as girls’ room, boys’ room, parents’ room (with babies). The girls’ room had two bunk beds with a 5th bed that went across between the two top bunks (so that they could put dressers beneath it. You have to get creative.
Generally speaking, though, our culture today is much more focused on accumulating “stuff”, and that stuff takes up a lot of space. When it comes down to it, we don’t need nearly as much space as we think we do.