Our house has 5 bedrooms, which is usually fine for us. My wife and I share one room, my 2 eldest daughters (15 and 12) share another, my step-daughter (15) and step-son (11) each have their own rooms and my youngest two (twins, age 5) share a room.
My eldest son (22) and his girlfriend are visiting for about a week. We don't have a spare room so the easiest option is for them to take my step-daughters room. She would share with DDs (15 and 12), but I'm worried it might be a bit uncomfortable for her having a step-brother she'd never lived with in her room.