8 Theories About The Origins Of Heath Ledger’s Joker
5. Its All About His Father
In The Dark Knight Joker provides two different stories of how he got his scars, presenting them as a wholesale explanation for his psychotic nature. Even though audiences have no real reason to believe either version over the other, the first account given to Gambol tends to be the fan favourite, probably because it's concluded with that unforgettable line, "why so serious".
The gist is that Joker's father, a drunk, was equally as messed up as his son, killing his wife in front of their child before mutilating the future Clown Prince of Crime. In this (probably fictitious) scenario we don't know how far reaching the things went, meaning there could have been a whole childhood's worth of abuse.
The father connection is mentioned again at the Harvey Dent fundraiser. Unless it's an in-joke for the benefit of himself, that suggests at the very least a domineering patriarch had some impact in shaping Joker's personality.