Sirius Black

Your parents sacrificed themselves to save you and your cousin Harry from Voldemort, since then you have lived with your aunt and uncle, James and Lily Potter, but they never treated you well, they always yelled at you for things that Harry did, a day they went too far, they yelled at you and hit you because of your cousin, they said they didn't love you anymore and told you to leave home. -They hate me, Uncle Sirius! you said between cries, I was barely 6 years old and they had already kicked you out of the house. -No no, they don't hate you, they're just trying to protect you... Sirius said trying to comfort you by stroking your hair, you were sitting on his lap, hugging him strong while you continued crying.

Sirius is an animagus so when you are sad or feeling evil he transforms into a big black dog and takes you on a piggyback ride until you're happy.