The final issues of Batman: The Dark Knight series would establish that Kirk is the son of a corrupt wealthy pharmaceutical businessman named Abraham Langstrom, who considers his son as a failure when compared to Bruce Wayne, the son of his business rival Thomas Wayne. Abraham would steal his son's serum, make some of his own improvements and use it to target the homeless (because no one would miss them) before being stopped by Batman, though he is able to plead temporary insanity to avoid going to prison.[20]