Adam Milligan was the biological half-brother of Sam and Dean Winchester, conceived in 1990 of John Winchester and Kate Milligan. He became Michael's vessel for the Apocalypse when Dean rejected the angels' plans, and he is currently trapped in Lucifer's cage.
Adam was conceived of John Winchester and Kate Milligan in January, 1990 when John and Kate met around the time John was hunting a ghoul. Adam was born nine months later, on 29 September. (Jump the Shark) Until he was 12, Adam had no contact with John, and thus he grew up without any paternal figure, and apparently mostly took care of himself while his mother worked graveyard shifts at the hospital. After John and Adam finally met, they had only sporadic contact; John taught Adam pool and poker, took him to ball games, bought him his first beer when he was 15, and taught him to drive the Impala. However, Adam didn't get to know John well due to the sporadic contact. (Point of No Return) In 2009, at the age of 18, Adam was studying at the University of Windom. (Jump the Shark)
Death by ghoulsEdit
In 2009, both Adam and his mother Kate were eaten alive and killed by a duo of ghouls seeking vengeance on John for killing their father. The ghouls afterwards stored Adam's remains within a coffin in their lair in a crypt, where Adam's corpse was discovered by his eldest half-brother Dean. After Dean and Sam killed the two ghouls responsible for the Milligans' deaths, they took Adam's corpse and gave him a hunter's funeral pyre. (Jump the Shark)
After Adam's death, his soul went to Heaven, where he eternally relived making out on his prom night; until a year after Adam died, angels came to him in his personal Heaven with an offer - Adam would be resurrected, under Zachariah's supervision, to serve on Earth as Michael's vessel for the battle against Lucifer, and in exchange, the angels would let Adam see his late mother again. Adam accepted, and was brought back to life on Earth, though not before the angels told him not to trust his half-brothers Sam and Dean if he saw them. However, when Adam was resurrected, Castiel came to investigate the angelic commotion, and killed the angel escorts sent for Adam. Cass immediately teleported the unconscious Adam to the Singer Auto Salvage Yard, and branded his ribs with angel-warding so that the angels couldn't track him.
After Adam woke up alive again, he initially tried to get away from Sam, Dean, Cass and Bobby so he could find Zachariah and consent to possession by Michael; Adam making clear that he didn't trust them, and that the fact they were blood was in his eyes no reason to consider them his family. Sam convinced Adam to just wait and bear with them for a while in honour of any good memories he had of John, and Adam reluctantly agreed; although this didn't stop Adam from unsuccessfully trying to sneak out several times, and it didn't stop Sam, Bobby and Cass from keeping him locked down and under constant watch.
Though Adam began to slightly warm up to and become more trustful of the Winchesters, when Zachariah contacted him in his dreams as he slept, Zach turned Adam back over to the angels' side by reminding him of their promise to him that he could see his mother again if he obeyed. Turned back over to the angels' plans by this, Adam gave Zachariah his location in the dream, allowing the angels to teleport Adam away to the Beautiful Room. Though Adam was expecting in the Beautiful Room to see Michael and say yes to him, he soon learned otherwise and how Zachariah had really been playing and using him - Zach's real plan was to hold Adam alive in the angels' custody, so as to use him as bait to lure Dean, Michael's true vessel, into a trap. Adam was furious that he'd been lied to and played, but was tortured into silence when Zachariah biokinetically caused him to internally hemorrhage.
Sam and Dean soon located the Beautiful Room and came for Adam as predicted, and Zachariah sent out an Enochian call to summon Michael now that Dean was where they needed him. However, Dean turned on and managed to kill Zach, and he, Sam and Adam then immediately set about getting out of the Beautiful Room before Michael arrived. Sam and Dean made it out, but Adam was trapped inside when the door sealed on him as Michael manifested. Before Sam and Dean could find a way to get Adam out, Michael took Adam away and vanished. (Point of No Return)
Michael's substitute SwordEdit
After Adam was taken away by Michael, with the angels' efforts to force Dean to say yes to Michael having failed too many times, Michael instead possessed Adam as a substitute vessel for his battle against Lucifer. (Two Minutes to Midnight) When the time of the battle finally arrived, Michael came to Stull Cemetery possessing Adam, but the battle was averted by Dean, Cass and Bobby's interference. As Sam threw himself with Lucifer inside him through the portal into Lucifer's cage, Michael intervened and tried to stop him, resulting in Michael/Adam getting pulled into the portal with Lucifer/Sam, and trapping the four of them in the cage together. (Swan Song)
A year and a half (in Earth time at least) after the Apocalypse was derailed, when Dean contacted Death to demand that he rescue Sam and Adam from the cage, Death agreed to rescue just one of Dean's brothers, and Dean chose Sam. Thus, while Sam's body and later his soul were brought back from Hell, Adam was presumably left to remain trapped in the cage with Michael and Lucifer. (Appointment in Samarra)
Currently, it is presumed that Adam and an insane Michael are now alone in the cage after Lucifer escaped again in 2015. (The Devil in the Details)
Adam was very much like his eldest brother Dean - he was cynical and blunt, very sarcastic and laid-back, and sometimes rather stubborn and rude. Adam also, as noted by Zachariah, had Dean's love for cheeseburgers. However, Adam didn't have as much belief as Sam and Dean in blood-ties, and felt that being his blood didn't make the Winchesters his family; due to which he didn't see John as a paternal figure, and felt that he'd never had any father. Adam was also less against and was accepting of and easy with fate and destiny and with the idea of becoming Michael's vessel for killing Lucifer, although he nevertheless did not appreciate nor tolerate being tricked or manipulated.
- Adam's birthday (29 September) coincides with the traditional celebration date of Michaelmas, which is ironic and possibly foreboding due to his possession by Michael.