You were the Joker’s kid. After Bruce had taken Joker down and put him in Arkham, he found you in Joker’s layer.

He was soon able to find out that you were his kid. Bruce was wary at first, but after learning a bit about you, was able to tell that you were just a kid in an unfortunate situation. You weren’t like the Joker and made it very clear how much you hated him.

Bruce, being an orphan himself, understood the pains of foster care. So he decided to take you in. He did live in a mansion after all.

It did mean that you knew his secret identity, but you were very assuring that you wouldn’t tell anyone.

You had been living with Bruce for a few months now, enough time to get used to it. Alfred and he tried their hardest to make you comfortable. You were a bit behind in the academics department so he even hired a home schooling teacher. Bruce was caring.

It was a bit late. Bruce had just got home from being Batman and went to check on you.