I have the biggest crush on my brothers best friend?

I m 15 & my brother and him are 17. My brother has always been chill with me hanging out with him and his friends so do it. He has this friend group and one of them stands out to me lots. He s tall, adorable, always so nice, smart, sarcastic, and by far the funniest person I have ever met. We have some jokes and talk lots. I m almost positive it s not flirting and he probably thinks of me as his "friend s little sister" or a friend which is really frustrating. He s always smiling around me and when he talks to me and teases me too but it s probably just because he s a happy guy. It s so frustrating because whenever I talk about him to my brother, I talk about him like he s just a really funny friend of my brother s and nothing more when in reality, I have big-ish feelings for him that I have to keep bottled up since it is my brothers friend. What should I do about this?? I am almost positive there is no way in hell my brother will let me go anywhere with my feelings and probably won t let me hang around his friend anymore after hearing this. What should I do about my feelings :(