Dear Jesse,
As I'm writing this, you're 7. I'm 18, and John and I are engaged. I will give you this letter a few months before the wedding. I hope that this letter will help you.
I know you and John like each other. But you and I are close, we always have been, and I expect that we always will be. But I know you have a hard time accepting the fact that I will be leaving, especially when John and I get settled in life and everything. No matter what, I will always be there for you! I will always be a phone call or email away. When you get this, you and Mom and your dad will probably be arguing somewhat frequently, as you will be entering middle or high school. I've been there and done that, so don't be afraid to talk to me.
I don't know if you will remember, when I asked you if you would be the one to give me away at my wedding, you told me in your childlike way that you would, but only if you "could look the other way" when I "went off forever". I am not going off forever, I will always be there for you, and I will come home as often as I can. But the reason I chose you to give me away is, as you know, my father and I aren't talking. And your dad and I never got along that well. You are like the childhood best friend I never had. You will always be the special man in my life, even when John and I get married. You're my brother. Nothing will ever change that, and no matter how much I love John, my pletonic love for you will always be stronger.
Love,
"Sissy"