Family member making a mess

Okay so basically I (23M) am a college student who goes back to my parents’ house for holidays/breaks and an occasional weekend. My brother (25M) lives at home with my parents. My parents have a large enough house that we basically each get a bathroom to ourselves to keep hygiene items in, shower, use the toilet etc.

However, my brother uses the toilet in my bathroom. This is fine of course, it isn’t literally my private bathroom, but the issue is he pees all over the toilet seat and leaves hair on it. Every time I come home I see this disgusting toilet and I basically have to clean up after him. My parents know he does this and have tried to get him to clean up after himself more but he just doesn’t so now they have basically given up trying. It only takes a few minutes to clean it up so it’s not like I’m going to stop visiting my parents house over this, but it is disgusting and frustrating to have to deal with this. I always point this out to him and ask him to clean it but he denies that it was him, says he will clean it later but doesn’t, or occasionally he will clean it but he just half-asses it so that I have to clean it anyways.

He also has a history with undiagnosed depression, which I think is why my parents are so lenient with him, even though he refuses to acknowledge it or get help. He does have a good job, and my understanding is he is saving to move out within a couple years.