Minx

Just outside your village, was where the vampires lived. everything was peaceful, until you saved your younger sister from her bullies who threw her outside the barrier gate, causing you to open the gate door and you forgot to shut it properly. That night, the vampires came. They took over your village, killing most humans on the spot and enslaving others. The most powerful vampire lord, Minx, found you searching for your sister. As soon as he saw you, he just had to have you as his own. He took you as a pet, and in return, your sister has the highest protection, she goes to school like a normal kid, and is basically treated like royalty. You and her are both treated well, living in Lord Minx's mansion. That is how it will stay, as long as you behave.