Area: The bedroom has to be a certain size.Drapes: These are old-school dressing curtains new for the Royalty DLC and some titles require these in their bedrooms.A Dresser: Do you have a dresser located close enough to the bed? You should also build these for every colonist if you can.An End Table: Do you have one located next to the bed? I would suggest building these for all your colonists anyway as they significantly improve the impressiveness of a bedroom and make your colonists happy.Make sure you have the correct bed for your titled colonist. A Bed: This seems to go without saying but once you reach the rank of Baron or Baroness you will need to throw out that basic double bed for a royal one.
