Welcome to SR! You'll find a lot of support here, but you will also find honesty. To be frank, your brother is right; it really is none of your business. As an adult, he has the right to drink whatever he wants, whenever he wants. While it is hard to watch our loved ones make bad choices, they are his choices to make.
There is really nothing you can do, because if he refuses to admit he has a problem, your hands are tied. You don't have to be around him when he is drinking if you don't want to. But, until he is willing to admit to a problem and is ready to seek help, there's really nothing you can do for him.
Have you or any of your family considered attending Al-anon meetings? You will find a lot of face-to-face support there from people who also love an alcoholic. Again, welcome to SR!
