I've never really said thank you for everything you do for me.
When you give a girl a brother, he'll support her in anything she does.
He'll run around throwing snowballs outside with her when she's a little kid, then go inside and make her hot chocolate. He will deal with her constant chatter on long car rides (and short!). He will even occasionally let her hang out with him when his friends are over, which she gives him major props for; since as a six year old, she wasn't easy to put up with.
As she gets older, he'll graduate high school, he'll leave for college, but he won't go far. She'll still see him on the weekends for lunch at the best hotdog place, and she's lucky because he later transfers back to her hometown, which means he'll stay at their house over breaks. And as long as he's in the house, she'll always have someone to blame for whatever she did wrong that day. Like putting cheese in the freezer, sorry for that by the way. He'll even still manage to find the time to bring her Harry Potter keychains from the local bookstore.
He'll graduate college, move away, and she'll start to grow up. She'll visit him, (he also conveniently lives by the beach) , and get a glimpse into his life and how he's doing. He won't share absolutely everything with his little sister, but they have fun together, so that's ok. When she's not visiting him, they'll FaceTime once in awhile, which is hard to make time for in their busy lives.
Eventually the whole family will be close together again, the family will get a little bigger, and she'll see him more often. They'll live under the same roof again for a little while and they'll somehow manage to share a bathroom. It isn't a huge disaster. He'll move out again, but he'll still give her the best advice, and she'll go over to his place when the "parental units" are just getting to be a little too much that day. They'll carve pumpkins and almost freeze their hands off trying to get all the guts out. They'll eat more garlic rolls than can ever be healthy for a person (like, ever). She'll see him work hard for what he wants, and set examples for her to do the same. She'll babysit the youngest members of the family as he once did for her, but she'll do it happily because she remembers how fun it was to hang out with a certain someone when she was that age.
As she gets older she'll realize more and more just how much her older brother has helped her. Superheroes don't always wear capes.
And she'll support him in anything he does.