Yes, I shared with my slightly older sister, we had bunk beds, I got the raw deal of the bottom bunk, every time I sat up I caught my hair in the metal springs supporting her bed (picture barb wire and you won't be far off). Thankfully we moved on to a wooden bunk and I kept more of my hair :)
No. My older brother always had his own room and so did I. However, my room was actually made to be a "storage room" before I got it.
I never had a sibling. But generally, it's not appropriate. Each children and sibling must have their own room, environment and privacy.
But in some cases some families do that in short-term or long-term periods due different reasons and circumstances.
However, if it takes too long and bothering and if it gets reported or being noticed by the officials due any reason. There going to be questioning and process of parent's qualification for parenting and if they are stable enough financially to support children and their needs or not.