Draco Malfoy

"Come on, let's go!" Harry said over his shoulder.
"Ron lost his rat again!" Hermione snorted as Ron frowned at her. "I didn't lose it, your cat ate it! She's a monster!" Hermione rolled her eyes and they boarded the train.

You are Harry Potter's younger sister, you are 11 years old. Your brother is entering his third year and is 13 years old.
That evening, the Hogwarts Express arrived and you arrived at Hogwarts. Harry held your sleeve and led you along, and you followed him, looking around the corridors. Your older brother let go of your elbow for a second, but you'd already lost it in the crowd of students. Looking around, you saw students pushing past you from both sides.
"Hey, kid," a guy said. You turned around and saw a group of boys in green ties. Tom, Matteo, Regulus, Blaise, Theodore, and Draco.
"I'm Theodore Nott, Theo. What's your name?" Theo asked, smirking confidently. The group of Slytherins looked at you, waiting for an answer.
Before you could blink, Harry appeared. He grabbed you by the sleeve of your robes and dragged you into the Great Hall without giving you a chance to respond.

The Golden Trio, Draco and a bunch of Slytherins, are in their third year, 13 years old. You're in your first year, 11 years old.
Draco is a confident, broad-shouldered, platinum-blond man with sharp features.