Since its introduction in the Batman: The Animated Series Season 1 Episode 22 "Joker's Favor" story, the Joker and Harley Quinn's relationship has been extremely popular, moving its way into both the comic and movie DC Universes. Despite its popularity, the relationship was blatantly toxic, with the clown prince of crime abusing Harley, manipulating her into a relationship when she was his psychiatrist at Arkham, and continuing the manipulation throughout their long-term relationship. The abusive nature of their relationship has led to Harley ending things and reforming in most universes, often teaming up with a combination of Poison Ivy, Catwoman, and the Bat-Family.
However, in two alternate universes, this deadly union resulted in the couple siring children. In both cases, Harley is forced to raise the children without the Joker, though each universe provides two very different reasons for his absence. Let's break down the two worlds where this deadly pairing resulted in the birth of their children.
Injustice
After Superman kills the Joker for murdering his pregnant wife Lois, Harley formed the "Joker Clan" who worshipped the fallen Joker and treated him as a martyr. Their anti-regime actions gained her trust with the insurgency, leading to Harley eventually reforming in the Injustice universe. In Tom Taylor, Juan Albarran, and Bruno Redondo's Injustice 2 #7 Harley reveals to Black Canary that she had a child, named Lucy, with the Joker years before who is being raised by her sister Delia Quinzel.
Harley says she gave Lucy up because she knew the Joker would never want a daughter and she didn't want to bring the baby into such a dangerous life. Harley returned to the Joker after being gone so long she thought it was a joke that he hadn't even noticed she was gone. Lucy also makes an appearance in the game Injustice 2 where it's revealed that she only knows her mom as an aunt, though Harley states her intentions to eventually reveal the truth.
White Knight
In the Murpheyverse where Batman: White Knight takes place, Harley left the Joker after enduring years of his abuse, with her breaking point being the murder of Jason Todd. After she left, Marian Drews snuck into Joker's life pretending to be Harley, to which the Joker didn't even notice the difference. After Joker was cured and went back to being Jack Napier he proposed to the fake Harley, only to have the real Harley return and knock out the imposter before joining Jack in his crusade against Batman.
During his time as Jack, the couple sired two children, a boy and a girl that remain unnamed. Harley is forced to raise them alone after Jack's death in Sean Murphy's Batman: Curse of the White Knight #6. In Katana Collins, Sean Murphy, and Matteo Scalera's Batman: White Knight Presents Harley Quinn Harley's life as a mother and raising her two children without their father will be explored in further detail.
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