Years after Gwen's death, it is revealed that Osborn had a one-night stand with Gwen, which led to Gwen's pregnancy with his illegitimate twin children. Osborn thus has three motives for killing Gwen; revenge against Spider-Man, to prevent Gwen from talking of their affair and creating a scandal, and to take their children to raise by himself, thus being his ideal heirs. Mary Jane was the only person who knew of their encounter and their children's existence prior to Gwen's death, despising Osborn for his immoral behaviors long before discovering he's the villainous Goblin. Gabriel and Sarah (who rapidly aged to adulthood years because of the Goblin formula in their genes) return to attack Peter as Osborn has the twins believe that Peter is the twins' father who abandoned the two and responsible for Gwen's death to which Peter learned the details of Gwen's past with Osborn and the twins from Mary Jane. Peter is able to convince Sarah of Osborn's villainy, the truth of Sarah's paternity and circumstances of Gwen's death, and stabilized the Goblin physiology with a blood transfusion due to Peter's blood type matching Sarah's. Meanwhile, Gabriel personally learns the truth of his relation to Osborn after watching a video message at one of the Goblin lairs, aligning with his father to stabilize his own condition using a variation of the Goblin formula at the cost of sanity.The Amazing Spider-Man #509-514 (Aug. 2004–Jan. 2005). Marvel Comics. All of this was retconned during the Sinister War story-arc, when AI version of Harry Osborn's mind reveals that he masterminded a plan to get revenge of both his father and Peter Parker: he created the twins in a lab with the help of Mendel Stromm and he brainwashed Norman and Mary Jane Watson (thanks to Mysterio) into believing Gwen cheated on Peter with Osborn. The twins aged rapidly because of clonation issues (and not because of Osborn's Goblin Serum), but eventually got better just as Harry started to use them as soldiers for his war against Norman and Spider-Man.The Amazing Spider-Man vol. 5 #73. Marvel Comics.
