K.J.
I shared a room with my sister from the time I was a few months old until she went away to college. When I followed her to college we shared a room again for another year.
My 3 brothers shared another room at the ages of 7, 2 and a baby. They all lived together in that room until my oldest brother went to college.
I think that we are generally pretty darn spoiled when it comes to every kid having their own room. It is not a necessity. I never felt "crowded" when I was growing up.