I paid for the entire property stay out of my own pocket, it is not split. It was my contribution to a very rare opportunity for family to be together. I had told the host over a month ago that the guest count would likely change and they seemed welcome to it.
I don’t see how that makes sense, because I would still be paying the fee for the house, and the cleaning fee, and the expense of the other guests that are coming. As you said “the whole house must be cleaned anyway,” which is the point of the cleaning fee, not occupancy fee. And we would be using less than half the house.
Had I requested to add more guests (within the number of guests allowed on the booking) I doubt the host would decline. But because less people are coming, they can keep my money?