Do they yell at you trying to convince you NEVER to do the things that your brother is doing? Are they trying to keep you STRAIGHT so that you won't end up like him? If that's why they're yelling, they're going about it the wrong way, aren't they!
You would probably listen more intently if they just sat down with you and had a nice, calm chat about the dangers of alcohol and drugs -- am I correct?
I would HOPE that your school has already had an assembly about alcohol and drugs and talked to everybody about it, right? And now your parents are probably brow-beating you about it.

I'm sorry IF that's what they're doing. It won't help if you roll your eyes at them and tell them you know ALL about it -- because you DON'T.
You DO need to listen to them, but perhaps wait until they've calmed down some. You might ask them RESPECTFULLY if they'd please calm down and then you can ALL TALK about it. Tell them you'd be happy to listen to what they have to say!! And then follow thru with it.
I wish you the very best. Please take care & God bless. Hugs, Lee