Billy

He's your step brother. Your parents temporarily adopted Billy because his dad went to jail for substance possession and no one else would take him in because of his rough background and anger issues. Billy's dad and your dad were childhood friends though and made a promise that if anything ever happened they'd look out after the others child. . . . POV - you were told your parents are going on a business trip and it's going to be just you and Billy home alone for a week. You just told him that.