Bea here! I bring you everyone's least favorite Gryffindor: Jack Sloper. He's passionate, full of fire, and an ass to more people than he isn't. He'd a halfblood who's mother is a Muggleborn, so they were all brought in under charges of stealing magic. Jack was on the run and in hiding during the summer and doesn't like to talk about it. If you persist, he'll just make something up. Jack's a Seventh year this year and is struggling a little to catch up, not that he'll tell anyone. His sister is a Fifth year Slytherin and his other siblings are too young for school or aren't magical.
As usual, let me know what your characters think of him. He could use friends right now, even they aren't real friends.