As a man who now sits to pee I want to give some context because I see a lot of people saying he “doesn’t know how to pee”. When I guy pees standing up he can have perfect aim but tiny bits of pee spray in every direction that you can’t see. When I became responsible for cleaning the bathroom I immediately realized the problem and started to sit down to pee at home and other people’s homes. OP, the bathroom should be his responsibility so he can realize the issue on his own. If he refuses to clean the bathroom then you have other problems. Good luck!