Hey hon. I think I know a little of your situation.
My sister and I are almost 6 years apart. All our lives, I was the kinda dorky one, the one that liked learning and got good grades, and worked hard for them. My sister was more into friends, and clothes, and parties, and boys. She had her first ‘boyfriend’ in kindergarten. I had my first when I was 19. So there you go.
I didn’t have very good parents, and it sort of fell on me to take care of the younger ones (we have a brother who is 2½ years younger than I am). I taught her to read, how to tie her shoes, how to wash her hair properly, all of that. I was her confidant for a while, until she got to high school and it was no longer “cool” to hang out with your big sister.
I love my sister to death, and it really pains me that we don’t get along as well as I’d like, but we are just very, very different people. And there’s nothing wrong with that, I suppose. I hope as we get older we can grow closer together – she’s 18 now, I’m 24. She’s still concerned with her boyfriends and her hair, and I’m still wishing she’d just read a damn book so I’d have something to talk with her about.
I suppose it all comes down to we both spent our lives being so damned stubborn that we never cared enough to learn about each other’s interests.
I suggest you try to find some time with her away from your parents and your brother. Maybe hit a spa and get mani/pedis together, or something. Ask her if she’d be interested in joining you at something you like, if you attend something she likes as well. You might find our you’re closer than you think.