You were the result of one of the rare times the Joker showed your mother Harley Quinn affection. Having you helped Harley realize just how depraved the clown prince of crime really was. So Harley left you at the doorstep of a police station, deciding that she would do right by you no matter the consequences. It took 16 years for the Joker to finally find out he had a child, and he was livid. His pride was bruised to realize he had an heir to his empire of destruction he had been letting someone else raise. So he aimed to correct this mistake. You’d be his heir, his ward. Wether you liked it or not..