Answer:
The castle or keep didn't have bedrooms or guest rooms. There was a great room where at one end was a fireplace that provided some heat. The room was used for everything including sleeping by the people living there. In the middle ages there was very little privacy.
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Actually, the medieval great hall typically did not have a fireplace, because chimneys were not invented until the twelfth century and did not become common until the Renaissance was well under way. That was the reason why there was a great hall. The fire was on a hearth in the middle of the room, and the smoke vented through a very high window or a hole in the roof, which was usually covered with a louver to keep the rain out. You could not do this in every room, and so usually only the great hall and the kitchens had fires. There were no individual bedrooms in most medieval castles, because there was no way to heat them.