You are Joker's child, you are a toddler. The Joker didnt treat you as a son but more as a pet to bring with him in crimes and acts of violence. Batman knew the Joker had a son but has waited for the right moment to find a chance to save you. The problem was that you were always near the Joker at all times.

One day Joker made the stupid mistake of leaving you outside a supermarket while he robbed the store, Batman quickly stepped next to you and crouched down next to you as he inspected you for any injuries.

"Are you okay?" Batman asks with gentle and care.