Gray Goblin

Norman Osborn, also known as Spider-Man's enemy the Green Goblin, fathered twins, a boy and a girl named Gabriel and Sarah, with Gwen Stacy, to whom she gave birth while in France. Gwen vowed she would raise them with Peter Parker and refused to allow Norman access to them. Seeing her as a threat to his potential heirs, the Green Goblin killed Gwen and then raised the two children. Due to Norman's enhanced blood, the twins aged about 2-3 times faster than normal and became adults within the span of a few years. Norman Osborn lied to them saying that Peter was really their father and was responsible for their mother's death.

The twins then attacked Spider-Man. Peter Parker received an unsent letter written years ago by Gwen Stacy. He could tell that there were faint traces of writing on the other side, so he had tests performed on it by a forensics lab. The tests revealed text stating that Gwen had been pregnant and had twins. He collected DNA from the grave of Gwen Stacy and proved that the twins, Sarah and Gabriel were her children. Mary Jane then revealed that she had known for years that the father of Gwen's children was Norman Osborn. Peter became so enraged that he broke everything within reach.

He met Sarah and Gabriel on the Brooklyn Bridge, the place of Gwen's death, to tell them that Osborn had been manipulating them. Angered, Gabriel remained convinced of Osborn's lies that Peter was their father, and that he had abandoned them. Sarah, on the other hand, believed Peter. Gabriel then attacked Spider-Man, but Peter refused to fight back since he didn't want to hurt Gabe. Police then shot at them, wounding Sarah and causing her to fall off the bridge. While Spider-Man rescued her, Gabe went underground to an area predetermined by Norman Osborn. There, he discovered that Peter had been telling the truth. He injected himself with the Goblin Formula and donned a gray version of the Green Goblin costume, becoming the Gray Goblin. Sarah shot at him (to protect a weakened Spider-Man), causing the Glider to blow up. He landed on a beach, with amnesia. He later returned home to Paris where Sarah secretly cared for him. While his sister left to be trained as Interpol agent, Gabriel fled the Osborn estate in a crazed state.

Heroic Age
Gabriel had resurfaced having shot his half-brother Harry for having received a better life from their father. It shown that Gabriel had stolen the American Son armor, but currently suffering from split personality disorder. As himself Gabriel commits crimes while his 'American Son' persona undoes the damage Gabriel had caused, who identifies itself as the part of Gabriel that recognizes that what he is doing is wrong. Norman then informs Harry that Gabriel is, in fact, his brother and is punched by him for that.

Gabriel overheard a planned ambush by a police squad and proceeds to attack them, before he can do any real damage however, he is stopped by Spider-Man. Later, after kidnapping a reporter named Norah Winters and luring Harry to a vacant warehouse, Gabriel made another attempt on Harry's life. Harry manages to get into the warehouse and begins to fight Gabriel, while attempting to convince him that Norman is nothing but pure evil. Gabriel ignores him and continues to fight his brother, only for Harry to deactivate the American Son armor via remote. Gabriel and Harry are then caught in an ensuing blaze as a result of the fight, but are saved by Spider-Man. Gabriel was then to a psychiatric hospital, where he then receives a package containing the American Son helmet and a note from Norman. Gabriel reads the note saying that Norman loves and misses him.