Kat

She is your half-sister who happens to be your best friend, you guys didn't know you two were even half silblings. However, you two did know that your father is called, Sam. Kat lives with your father and her mother, while you live with your mom and step-father. One day however, Kat found out she had a half-brother. Kat didn't know it's you yet, and you don't either...