I'm Sirius's daughter (believed)

"I'm Sirius Black's daughter," Harry said, embroidering the story as she went. "My mother kept me hidden after he was arrested, that's why I never went to Hogwarts. I don't know if he actually knew I existed, Mother never said."

Malfoy smiled. "In that case... It seems we are cousins. I'm Draco Malfoy, Narcissa's son."

"Pleased to meet you, Draco Malfoy," Harry replied, smiling herself at the absurdity of the situation.

Malfoy smirked. "Come on, let's head back to the Manor. Mum'll be ecstatic to meet you... and probably annoyed as hell at old Walburga for blasting Sirius off the family tree. If she hadn't done that, we might have known you existed, and you could have been brought up in the luxury you deserve. Even as a half-blood, you're still Sirius's rightful heir... are you half-Muggle or half-Mud... Muggleborn? I'm sure we can work with even the former, but it'll be better for you if your mother is at least a witch."

"Yes, she was a witch," Harry replied. "But what if I don't want to come back with you?" she added, hand drifting towards her wand.

"Don't be foolish," Malfoy continued, the threat under his faux-cheerful tone becoming more visible. "I can't very well let my cousin and the rightful heir to the house of Black run around rogue like this. And given that your mother can only technically have been a witch, I can hardly trust your loyalties without further proof, now can I?"