Dupli-Kate's power is mystical in origin. The result of an ancient Chinese curse by the Emperor against his usurper, the Warlord Fung Cha, moments before his death. The curse was: "The seventh generation after Cha's seventh grandchild would be burdended with a family too large to care for... and it would drive him mad."
Hundreds of years later and the appointed grandchild gives birth to twins, Paul and Kate. As toddlers they began to multiply uncontrollably and eventually fulfilled the curse driving the father Tsing Cha mad.
At puberty the twins gained control of their powers and can now generate and absorb duplicates at will. Multi-Paul, as Paul was called, kept himself hidden until Kate's death was public knowledge, then he starts a murderous rampage against Rex Splode and Invincible, holding them responsible for Kate's demise.
Dupli-Kate became a member of the Teen Team, where she was involved in the breakup of Rex Splode and Atom Eve after Eve walked in on Rex cheating with multiple copies of Kate. Along with her fellow Teen Team teammates, Robot and Rex Splode, Kate joined the new Guardians of the Globe after the old Guardians were murdered. Rex later found Kate cheating on him with the Immortal. Kate's relationship with the Immortal grew more serious and after a brief engagement they were married in a private ceremony.
In a recent fight with the Lizard League, Kate was apparently killed until issue #46 of Invincible, Dupli-Kate appears stating that she had her original self hidden away for protection. When "she" died during the fight with the Lizard League, only the copies died while her original self was somewhere undisclosed.
She returns to stop Paul's rampage, only to find that Invincible came first, and refusing to hear her pleas, wants to put Paul in jail.