There are different rules about ages and gender of kids that can be in the same bedroom. Also, you can have a baby in your bedroom if you are a foster parent, they can't sleep in your bed though.
I only have a 3 bedroom house. I have me, my husband and my baby girl in our room. My son and our adoptive son will share a room, and then my daughter and the two adoptive daughters will share a bedroom.
That is a lot of people in a 3 bedroom house! Here's hoping that something crazy happens and a bigger house is in our future!!!
(We have a finished basement so we are thinking about putting a bedroom down there as well. We actually have room for 2-3 bedrooms down there, but we shall see)