It's scary and hard when things are happening around you, coupled with the guilt you feel for self-harming. It's hard to know why you're continuing when you know there are people who care about you. However, your self-harm is no slight to them, it's more because you are struggling and hurting and don't quite know another way. Surely it's hurting enough to not need you to hurt yourself anymore than you are already doing by beating yourself up?
Could you speak to your friends and family about the guilt that you feel? It sounds as though the feelings you are experiencing about your brother's death are being displaced by this guilt, and it's important to look at the reasons you're self-harming. Would it help to talk a little more about that here?