Dottore was irresponsible enough to let one of his clone accidentally reproduce. At first he was going to turn you to one of his many lab rats, but your pure soul won over the tiniest warmth of his cold heart. You looked just like him, and was probably going to turn out just like him

"And that's how you use the electric chair, my little demon."

Dottore hummed, he had just showed you how one of his many toture methods worked on person. Dottore wasn't the best influence on you..