Batman / Batman Joker

Does Batman Know Joker Is His Brother?

The relationship between Batman and the Joker has been a topic of great debate among comic book fans for decades. One theory that has gained traction in recent years is the idea that the Joker might actually be Batman’s long-lost brother.

But is there any truth to this theory? Let’s dive in and explore.

Origins of the Theory

The theory that Batman and the Joker are brothers first started to gain popularity after the release of “Batman: The Killing Joke” in 1988. In this graphic novel, the Joker tells Batman that they are “two sides of the same coin” and that “if [they] didn’t exist, [they] would have to invent each other.” This led many fans to speculate that there might be a deeper connection between the two characters.

Clues in Comic Book Canon

While there is no definitive answer to whether or not Batman and the Joker are related, there are several clues within comic book canon that could support this theory. For example:

  • In “Batman: Europa,” it is revealed that both Bruce Wayne (Batman) and Jack Napier (the man who would become the Joker) were exposed to a deadly virus while traveling in Europe together as teenagers.
  • In “Batman: White Knight,” it is suggested that Jack Napier might actually be a long-lost Wayne relative.
  • In “The Return of Bruce Wayne,” Bruce travels through time and interacts with several versions of himself, including one who becomes a jester-like character known as “The Bat-Man.” This character bears a striking resemblance to the Joker.


Of course, not everyone believes that Batman and the Joker are related. Some argue that any similarities between them are simply coincidences or storytelling devices meant to emphasize their oppositional natures. Others point out that the Joker’s true identity has always been shrouded in mystery, and that it’s unlikely that he and Batman are related given the lack of evidence.


So, does Batman know that the Joker is his brother? Ultimately, the answer is unclear.

While there are certainly clues within comic book canon that could support this theory, there is no definitive proof one way or the other. Regardless of whether or not they are related by blood, however, one thing is certain: Batman and the Joker will always be two of the most fascinating and iconic characters in comic book history.


  • “Batman: The Killing Joke” by Alan Moore
  • “Batman: Europa” by Brian Azzarello and Matteo Casali
  • “Batman: White Knight” by Sean Murphy
  • “The Return of Bruce Wayne” by Grant Morrison