Should I ask my male roommate to pee sitting down?

My cousin (male, 20 years old) moved in with me earlier this year. He plays junior hockey, and was traded mid-season to the team in my city. It happened quickly and was just easier for him to move in with me. We’re roommates, essentially.

We have our own separate living areas, but are forced to share a bathroom. At first, everything was great. But after around 1 month of him living here, I started noticing an issue in the bathroom. The floor around the toilet started turning yellow and getting sticky. Also, the wall beside the toilet also started to slowly turn yellow and get sticky and smelly. This is happening because he pees standing up. I have made him aware of the issue, but he is still choosing to stand when he pees.

I really want to ask him to pee sitting down but I don’t know how he’ll take it, and I’m not the best a handling conflict.

Should I ask my male roommate to pee sitting down?
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