You obviously see your behavior as wrong and this can be a positive thing.
Is there some reason that you hate your step father? Has he done something to you? Or is it that you feel that he takes up your mother's time and you feel left out? It is normal to feel jealousy when one of your parents re-marries. There is an adjustment period and children will sometimes act out. However, this is not justification for willing "attempting" to hurt your own brother. That is totally inappropriate and you should STOP immediately. You could seriously injure him and you could end up in a juvenile facility. Think of the emotional damage you're doing to him and yourself.
I think you should discuss these things with your mother. Open up to her about how you're feeling. If you can't do it one on one, try writing her an honest letter. If this isn't an option for you, seek help from a guidance counselor, school psychologist, or even a trusted friends parent. Let someone help you to help yourself.
As far as demanding attention from the wrong people... you know and understand that you are doing this.... that is another positive. Are you seeking attention from these people because you're not getting your needs met at home? Or do you just feel the need for excessive attention, admiration, adoration, etc... but, don't really care where you get it? Another reason to talk to a trusted adult.
Children who are searching for attention will do almost anything to get it. Whether that be positive or negative. It seems to me, that the negative isn't working out for you so well. Why not try to put a positive spin on your situation? You seem willing to admit that you need help. Believe it or not, that is a step in the right direction. Please be kind to yourself. Give yourself some credit for admitting to your behavior. Trust that you mother wants you to be a happy, healthy, productive person. Allow yourself to become all of those things. My thoughts and prayers are with you.
Take care and God bless.
