I want to comment on the double standard that you spoke about in your initial post. I have two kids, one 17 and one 13. The 17 year old is a golden child. Everything he touches seems to work out. He is a 4.0 student. He is well liked by his peers. He does everything right, it seems. My 13 year old is a disaster academically (even though he is very bright). He has severe learning disabilities. He has to work hard just to get a 2.0. In fact, this year I am pulling him out of school for homeschooling - but that is another post.
Do I have a double standard? Absolutely. My expectations are totally different for both of my kids. Do I love one more than the other. Absolutely, not. They will both tell you that I favor the other one because I make/don’t make/allow them/ don’t allow them them do specific things. I don’t favor either. I ask them to do what I feel they can handle no more. no less, and what they can each handle is different, in terms of homework, in terms of chores, in terms of life.
Your parents might expect more from you because they know you can give more. This might get magnified. They may feel that you should to be able to do better because of the stark difference between you and your brother. The more they lower their expectations for him, the more they raise yours, because you seem so much more capable.
If your brother is really not as bright and as accomplished as you then they may really be looking toward you to make them proud. That is unnecessary pressure but they may see you as their success and your brother as well, their lack of success.
I would imagine that if your brother were to post on this forum, we may see someone stating that their older sister gets all the attention because his parents don’t believe in him. They think she is wonderful, while he was a failure. The she gets to apply to all these great colleges while he is not expected to go anywhere wonderful. It would be interesting to see the world from his eyes. I bet you would be surprised.