Supernatural is a TV show that began in 2005 on the network known as The WB. The show's life was in the balance when the network merged with another and became The CW. After two successful seasons on the air and a huge fan base developed, the creator Eric Kripke launched the comic. The comic series is a prequel to the show and is titled Supernatural: Origins.
Sam Winchester was born May 2, 1983 to John Winchester and Mary Winchester and has a brother four years his senior named Dean Winchester. In the comic series, Sam first appears as a baby and then by issue #2 he's about six years old. During this time Sam has not developed any of his weaponry or psychic powers but since the TV series shows us Sam in the future, those traits are part of his character since Mary's unusual death in their Lawrence, Kansas home.
Several six-month-old children across the country experienced the exact same demon encounter as Sam: a fire in their nursery and someone was killed by a yellow-eyed demon; in Sam's case it's his mother Mary. (The comic series to date has not disclosed this unusual supernatural activity as being a national event.) When Mary died, Sam's father John became obsessed and entered into the supernatural lifestyle to hunt for her killer, the yellow-eyed demon. John couldn't trust anyone and felt the boys would simply not be safe with another family member.
Sam is the younger brother and though he often seen crying or feeling insecure, he actually is a very strong individual capable of surviving without his father's or big brother Dean's protection. Dean was not touched by magic and does not possess the psychic abilities that Sam has. It's uncertain how much of this will be seen in the comic.
In issue #2, John finally meets the mentor he needs to keep himself and the boys alive. Unfortunately it's not until a Hellhound kills Mary's brother Jacob who had been tracking John and the boys.
It later revealed the Helllhound belongs to Azazel better known as the Yellow-Eyed Demon.
Sam's psychic powers are no coincidence and he wasn't born under a lucky star either. They originate from the events that led his mother's death. When Sam was six months old Azazel visited his crib at night and gave him some drops of his blood kinda like a Satanic baptism. When Mary realized it wasn't her husband in the room but recognized Azazel by his yellow eyes and attempted to interrupt the offering of blood Azazel pinned her to the wall telekinetically and then used his mind to move her upwards to the ceiling right above Sam's crib.
Using his mind again he slit her abdomen when john entered the room Azazel was already gone but Mary's body was still clinging to the wall the moment john gazed at her body a flame originated from her back and consumed the entire house. However Castiel offers Dean a chance to fully understand the grand picture by sending him back in time. The he finds out Azazel could not have performed the blood rite without being invited in via a deal which Mary made many years back in order to save johns life.
Later on Sam learns to control his powers on a much higher level he can now exorcise demons using his mind and send them to hell. Recently through "special" training with Ruby Sam has shown immunity towards Alastor's telekinesis he even sent the telekinetic attack back at him and them pulled him out of his body. Later on its revealed how Sam is getting stronger with his powers, by feeding off of Ruby's blood his powers and strength increase this also seems to increase his cruelty. Another power Sam has awakened by all of this is the power to psychically kill demons as displayed when he said "I'm stronger then that now, now I can kill." And used that power to kill Alastair.
Later on in season five of Supernatural Lucifer comes to Sam in a dream asking him where he is as he can no longer find him or Dean due to Castiel's Enochian Sigils enscribed on their ribs. He explains that the vessel he is wearing Nick is an improve and that he is his true Vessel. Sam refused to give Lucifer his consent which he replies saying he will never hurt Sam and never lie to him but he will say yes eventually and disappears. Later Sam confronts Famine who tells him he will never die from drinking to much demon blood he is the exception that proves the rule just like Lucifer wanted him to be. This also confirms that Sam's hunger for Demon Blood is ceaseless and can be picked off where he left off meaning there is no real detox from his hunger as it is part of what makes him Lucifer's vessel.
At the end of the season Sam says yes to lucifer, but this is only to take control of the possession and walk into the cage that Sam sprang Lucifer out of in the first place. At first this failed with Lucifer taking direct control over him he closed the door to the cage taking the Horsemen's rings with him. He then appeared on the battleground preparing to fight his younger brother Adam who had said yes to Michael and was now possessed by him. At the last minute Dean showed up, attempting to talk to Sam inside of him despite the possession. This failed horribly as Sam now Lucifer tore him down and was just about to kill him when the 1967 Chevy Impala sprang reflective sunlight into his eye triggering a series of memories to flow into his mind and was reminded of who he really was Sam Winchester. He then opened the Cage using the Enochian spell only to have Adam/Michael try to stop him saying it was his destiny to kill Lucifer leaving both of them jumping in the pit as Adam grabbed hold of Sam as he fell inside forever trapping both the Devil and Michael inside along with their vessels Sam Winchester, and Adam Winchester. Sam later appeared beneath a blown out street light peering at his brothers free life from hunting with a family of his own.