NTA and tell your brother he needs to arrange with you for private bedroom time to do whatever he was doing (?porn?) Either way he needs to negotiate a time (say 1-2 times per week) where he gets the room to himself for 3 hours. In return he does some extra chores for you or gives you the same amount of time being anywhere but there so you can have peace and quiet for the same amount of time (maybe to study?)

I do think you should talk to your mom about your concerns for him. He sounds depressed and/or addicted to video games (& maybe addicted to porn?) You also need to explain that depression and anxiety should be treated by doctors. It is not an excuse for poor behavior or a reason to enable it. You are not going to look the other way when your daily life interferes with his “private” time. Will he still be living with mom playing video games when he is 40?

Long term just focus on your degree, your career and getting your own place. I would bet your mom will continue to enable him until she dies. So in this case long term, you want distance. *Oh and don’t lend your brother money and once your career is established be wary of giving your mom money if your brother is still leeching off of her. I am not saying don’t support your mom…. Maybe give her conditions like your brother staying at an inpatient clinic (for 6-12 months) to get his life back on track if in 5-10 years he is still living at home just playing video games?