There's been a mystery around Thor's true parentage since the story Avengers: Enter the Phoenix, in which the Phoenix Force told Thor that she is his mother and that the history he's been told by his father Odin is a lie.
Now, in Avengers 1,000,000 BC #1 from regular Avengers series writer Jason Aaron and artists Kev Walker and Dean White, the secret of Thor's true lineage and the Phoenix Force's involvement in Thor's birth is revealed.
Spoilers ahead for Avengers 1,000,000 BC #1(opens in new tab)
Throughout Avengers 1,000,000 BC #1, we're shown glimpses of Odin and the Phoenix Force's courtship, in which Odin's brash, blustering nature quickly alienates the Phoenix. Still, Odin persists in trying to forge a union with her, even staging a surprise wedding with all the other members of the 1,000,000 BC Avengers in attendance - which Phoenix once again spurns, leaving in anger.
Later, we cut to the scene of Thor's birth, as Gaea, the Earth goddess, is attended to while she gives birth. Odin drunkenly arrives, awaiting the celebration of his new child, essentially confirming that Odin and Gaea are indeed Thor's birth parents as he has always believed.
But things aren't gonna be that simple.
First, there's a flashback between Gaea and the Phoenix Force, which starts to imply that the Phoenix may have seeded life in Gaea's womb herself - but as it turns out, the Phoenix Force actually encourages Gaea to get together with Odin, foreseeing that the child produced of their union would be a great protector for the Earth.(opens in new tab)
With Phoenix's words ringing in her ears, Gaea accepts Odin's advances, and Thor is eventually born. But flashing back to the moment of Thor's birth, the frost giant Laufey - birth father of Loki - arrives to murder the child to get revenge on Odin and the Avengers for an earlier defeat.
Though the Avengers are able to hold Laufey back, the bitter cold brought on by his attack is enough to seemingly kill the newborn Thor.
However, the Phoenix Force swoops in at the last moment, snatching the infant Thor and whisking him far away from the battlefield, and using her flame of rebirth, manages to revive him - revealing her actual involvement in Thor's birth as his protector, and something of a second mother or life-giver.
So there you have it: Thor is indeed the child of Odin and Gaea, a union made possible by the intervention of the Phoenix Force, who also magically saved Thor's life as an infant.
The story continues in AXE: Judgment Day tie-in Avengers #60, on sale August 24.
Thor is one of the best Avengers members of all time.