What if the joker is Batman's dad!
Let's say on that night where his parents were shot.. And they didn't die.. they just suffered severe 'led poisoning'. And led poisoning has been medically confirmed to cause acute memory loss as well as schizophrenia... In the graphic novel The Killing Joke, it reveals a very concrete backstory to the joker.. he was just a regular man with a loving wife... What if these two were Thomas and Martha Wayne, Bruce's parents.. who have no recollection of their life before they were shot
And those of you who are thinking if the joker was batman's dad. Wouldn't he look much older... Well the joker has permanent dimples and wrinkles all over his pale white face. And permanent green hair. So its hard to tell how old he is...
And batman won't kill him because he subconsciously knows it's his father.