Help!!! Who should share a room?

My husband and I have 4 kids. Three daughters (7,5,2) and a son that’s 6 months old. We just purchased a spacious 4 bed, two bath home. Our issue is that we don’t know how to arrange the rooms. Who should share a room? Does our son automatically get his own room because he’s the only boy? Prior to moving our son slept in our room, but shared a closet with our oldest. How would you arrange the rooms? All advice welcomed! We want to be as fair as possible.