5 or 7+ bedroom houseboat is given as a sharing basis, each couple will get separate rooms with the attached bathroom in one houseboat. They can share a common lobby, dining area, top floor, sun deck etc, this is called a sharing houseboat.
Just think that you are staying at a 3-star hotel. You are getting a private room and you go to a common restaurant to dining. Similar way you are staying houseboat which is floating/cruising and you can hang out around the houseboat just like a hotel. There is enough space for all guests. The upper deck area is commonly using for dining purposes.