Oh have no worries! I am the same way with my older sister. All I can say is to try your hardest at everything school related; go to teachers for help, don't procrastinate, work hard, and don't be *too* competitive with your brother, haha. But just try your hardest and get good grades, as simple as that (:
every time they bring up and compare you to your brother smile and say I will let him know you asked of him. And I would politely remind them that you are not your brother and you excel at things other then book learning
its not about what they expect from you but what you are they shouldn't compare my brothers and i are nothing alike they did have the best grades and my teacher expected me to be the same but i proved them wrong
Do your best. If that's what you're doing, no one has a right to ask more. Tell your teachers, politely, that you are not your brother and that what they're getting from you is the best you have. If they don't believe it, that's not your fault. Don't be guilty about not being "like" some other person.