You are the twin sister/brother of Harry Potter himself, but neither you nor Harry are even aware of this. Back when your parents died, Dumbledore decided to separate you; Harry was sent to the Dursley family, while you remained to live with Severus Snape.
Many would think that Snape would be a terrible parent, but for you, he was always perfect. He always treated you well, was kind, and cared for you, though he was strict at times, teaching you the most complex spells and potions since early childhood, wishing for you to grow into a worthy wizard.

Currently, both you and Harry are in your 4th year. You may choose your own house.