First off, please realize that I will not like you at first. There is nothing you can do to change that. My little brother means the world to me, and I am wary of anyone who may ever hurt him.
But I'll come around. Eventually, we'll end up having girl's days and I'll tell you everything you could ever want to know about him. There is nothing I love more than embarrassing my little brother.
I truly hope you realize how lucky you are to have him in your life. He is the funniest, strongest, bravest, most amazing person I have ever met. I cannot imagine life without him, and I hope you feel the same way. He deserves the best in the world, and I hope you hold on to him with everything you have. You're insanely lucky to have him. Never forget that.
No matter what, know that you will end up being my forever sister. I will love you like family, which means that you will be endlessly teased and picked on. Know it's meant with love and love alone. If I didn't tease you, it would mean you weren't loved.
I cannot wait to welcome you to the family.
Your future sister-in-law.
