My father-in-law brushes his teeth in my house and prefers to wash dishes in the kitchen rather than the washbasin in the bathroom. Should I say something?

Come on, personally, I feel I have to say that this is a matter of living hygiene principles and cannot be ignored. Non-principled issues can be ignored, and such principled issues cannot be compromised. In fact, you can find an opportunity to bring it up politely. As long as you get to the point, people who believe in understanding will understand your meaning. From a certain point of view, you are the owner of the house, and you are the person with a general direction in the family. All the planning and life goals at home revolve around your design, and your ideas are being operated and implemented. The old man is just helping you realize family planning now. No matter what the old man does, as long as you think it is right, everyone should carry it out. If you sort out these things, I believe you won't be entangled in such things.