Adam Milligan

Adam Milligan is the son of John Winchester and Kate Milligan, and half-brother to Sam and Dean Winchester.

Early Life
In January 1990, Adam's mother met John Winchester in Windom, Minnesota when he came into the hospital where she worked as a nurse, when he was injured during a hunt. Adam was born on September 29, 1990. He didn't have any contact with John until he was twelve. That same year, John killed a ghoul.

After the initial meeting, he had sporadic contact with John who taught him pool and poker, took him to ball games on his birthday, bought him his first beer when he was 15 and taught him to drive in the Impala. In 2009 he was studying pre-med at the University of Wisconsin.

Years later, seeking vengeance, the ghoul's children killed Kate and Adam Milligan and assumed their forms, hoping to lure John into a trap.

Season 4
In "Jump the Shark", "Adam's" call reaches Dean and Sam instead, as John died two years earlier. Dean and Sam discover the trick, kill the two ghouls, and burn the body of the brother they had never known. Dean says he was their brother and died like a hunter, so he deserved the funeral of one.

Season 5
Whilst enjoying eternity in his own private Heaven (making out on his Prom night) Adam is approached by Angels who offer him the opportunity to help the Archangel Michael defeat Lucifer by becoming Michael's vessel. Adam accepts and is resurrected under Zachariah's supervision. He awakes beneath the ground where his funeral pyre was held and crawls to the surface to find Castiel waiting for him, the angels originally meant to greet him lying dead nearby. Castiel teleports Adam to Bobby Singer's house, much to the amazement of Sam and Dean.

When he regains consciousness, Adam informs the Winchesters of his deal with the angels and his intention to say "yes" to Michael. However, Castiel engraves Enochian runes on his ribs to keep the angels from locating him. Though they are confused as to how Adam can qualify as a vessel for Michael, Castiel deduces that because Adam is of the Winchester bloodline he is eligible to contain Michael's essence, despite the prophecy that foretells Dean as the one and only candidate. However, Dean doesn't want him to share that fate and slips away.

Sam leaves Adam in Bobby's care while he searches for Dean. Meanwhile, Adam dreams of the park his mother used to take him to when he was little and is greeted by Zachariah, who convinces Adam that the Winchesters are not to be trusted and that if he cooperates with the angels he will get to see his mother again. Adam gives Zachariah his location and the angels promptly snatch him out from under Bobby's nose.

They take him to the Green Room where they had imprisoned Dean and Zachariah reveals that he has been lying to Adam all along. Adam's sole purpose is to lure Dean into a position where he would have to say yes to Michael, which proves successful when the Winchesters arrive to rescue their brother. Zachariah tortures Adam and Sam until Dean agrees to becoming the vessel, but this is a ruse as Dean provokes Zachariah into letting his guard down and uses the chance to stab the him with an angel knife killing him instantly.

Dean and Sam escape the room just as Michael descends but the door slams shut behind them, trapping Adam in the room with Michael's true form. Dean smashes the door open to find the room gone along with Adam and Michael.

In "Two Minutes to Midnight", Castiel tells Dean, Sam and Bobby that Michael is currently using Adam as his vessel.

In "Swan Song", Michael, in Adam's body, facing off against Lucifer in Kansas. When Lucifer tries to convince Michael to join him and rebel against Heaven, Michael refuses and prepares to fight his brother until Dean loudly enters the cemetary with the Impala. Before either Archangel can act, Castiel uses a molotov cocktail of Holy Fire on Michael, banishing him from the cemetary for a time. Lucifer then destroys Castiel for this act. As Sam regains control of his body and is about to jump into Lucifer's Cage, Michael tries to stop him and both end up falling in. Due to Sam's release from Hell Adam's own status is unknown, but it is presumed he and Michael are both still trapped in the Cage.

Season 6
In "Appointment In Samarra", Dean tries to make a deal with Death to retrieve both Sam's and Adam's souls from Lucifer's Cage, but Death says that Dean can only pick one. Dean picks Sam, inevitably leaving Adam trapped in the Cage with Lucifer and Michael, where he remains now.

Trivia

 * Adam's birthday coincides with the traditional date of the Feast of Saint Michael, or Michaelmas.
 * Adam was twelve years old when John Winchester made contact with him. Mathematically, this would be the same year Sam Winchester left home for Stanford. This could also mean that John pursued a father-son relationship with Adam to replace Sam.
 * Adam's role as a third son of John Winchester is similar to the character Leinad, the protagonist of the Christian Allegorical novels known as The Kingdom Series, who is a supposed allegory to a third son of Adam (Bible). Their personalities differ greatly though.
 * By extension, and perhaps as a better reference, Adam's role as a third Winchester son reflects that of biblical Seth, the younger brother of both Cain and Abel.
 * Is currently sealed in Lucifer's Cage, along with the Archangels Michael, Lucifer and Sam, until the latter was retrieved from the Cage in two parts: body first, then soul, which makes Adam the only human/vessel left in the Cage.
 * The back of Adam's head was shown in a flash-image during the Season 8 Man's Best Friend With Benefits, when Spencer hit Sam with images from within Sam's own mind.

Season 4

 * "Jump the Shark" (corpse)

Season 5

 * "Point of No Return"
 * "Swan Song" (As Michael's vessel)

Season 6

 * "The Man Who Would Be King" (Flashback as Michael's vessel)

Adam Milligan アダム・ミリガン