5 or 7+ bedroom houseboat is given as sharing basis, each couple will get separate rooms with 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 3-star hotel. You are getting a private room and you go for 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. Upper deck area is commonly using for dining purpose.