Yet i don't now his real orgin but here is my fan theorie. He had an abusive father and his mom was getting abused to so they both abused him. Even though he hated them he loved them to. He much like batman witnesses his familys murder and gets away but he was on the bad part of town so he had no offiser gorden to help him turning this teenager in to the joker we love.
Haveing no money much like most comic book villains resorts to crime and thieves. He laughs becuse he needs something so he doesn't go insane but he does.
So thats his story my version. Like it share it add me on Facebook