Rather than the advice most offer..."stick in there", "life isn't so bad", etc. Here's the pulse. Life can always get worse, always. That's a promise, but on the flip side...life can and will get better with positive thinking and motivating yourself to control your life. Guess what...you already do. Nobody controls how you feel. Nobody, but you. If you wanna feel better about yourself, write down 3 things your proud of every day. Doesn't matter what they are, just write them down and tell SOMEBODY. Doesn't matter who, a teacher, a counselor, your dog, a stranger.
Here's the other part aside from all that, talk to someone that is a licensed professional. It helps, I promise. I've been there, and the professionals don't spend many years getting a masters because it doesn't work. Don't just talk to them though, talk to your parents. They might favor your brother, but most parents love their children reguardless of favoritism. Tell them that you have a real problem, that you're depressed, and that you need help. If they ignore you or brush it off, then speak to your school guidance counselor to get some backup from someone to support you. Support helps in all cases of depression. That's the best I got. Don't just bottle up and hope things will get better. You...YOU...have to take action to help yourself. Nobody can help you if you aren't willing to do something to help yourself.