Eddard Stark's illegitimate bastard son by an unknown mother, brought home after Robert's Rebellion. Jon has felt like an outsider among the Starks since he was very young, when he learned what it meant to be a bastard and thus why he was Catelyn's unfavorite among the children. The experience made him bitter and left him with a desire to prove himself. When his father leaves Winterfell, he chooses a life of hard duty in the Night's Watch to earn his own honor, he is chosen by the Lord Commander to be his personal squire, in other words he is being groomed for command.
In the television series 'Game of Thrones', Jon Snow Portrayed by British actor Kit Harington, first appears in the episode 'Winter is Coming'. He becomes a major character within the honorable House of Stark. He is the bastard son of Lord Eddard Stark of Winterfell, Jon's mother remains a mystery. However, Eddard did mention to King Robert Baratheon that the name of Jon's mother was Wylla, a serving girl. Eddard did have the intention to reveal this to Jon upon their next meeting, but never had the chance due to tragic events and the leading to Eddard's death.
Jon Snow is a strong and very accomplished swordsman, along with other combat skills. In Season 1, Lord Commander Jeor Mormont of The Night's Watch was attacked by a Wight in his quarters, Jon Snow came to his rescue and killed the Wight. As a reward for saving his life, Jon was presented with a sword, Longclaw.
Longclaw is of Valyrian steel and has been in The House of Mormont for 5 centuries, Lord Commander Jeor Mormont before handed down Longclaw to his son, but the sword was sent back to him due to his son's dishonorable actions. The Lord Commander made changes to Longclaw, he replaced the pommel of the sword with a direwolf instead of a bear in honor of Jon Snow's sigil House of Stark. It should be noted Valyrian steel is one of few things that can destroy White Walkers, alongside dragonglass, as discovered by Jon during the attack on Hardhome.
Though Jon may be the only illegitimate child of Eddard, he was raised among his other children as equals. He is the half brother to Robb, Sansa, Arya, Bran and Rickon. Jon has a strong bond with older brother Robb, younger sister Arya and younger brother Bran.
His relationship with his stepmother, Lady Catelyn Stark was anything but loving as he was a constant reminder of Eddard's infidelity to her.
Jon Snow has an animal companion, a direwolf he named Ghost. Found next to a dead direwolf along with 5 other pups, Jon believed it to be a good sign from the Gods as there was a pup for each of the Stark children. He opted for the runt of the pack as the pup was the odd one out, due to its color.
Once Jon became part of the Night's Watch, he befriends several recruits Pypar who was sent to the wall for stealing (but really because a lord tried to touch him), Grenn an orphaned farmer. Later he meets Samwell of the House Tarly. Sam is an overweight and unskilled fellow Night's Watchmen, but he proves himself well read and kind hearted. Jon takes it upon himself to protect Sam from others tormenting him.
Jon Snow encounters himself with a Wildling, named Ygritte, In Season 2. She was captured in a result of a failed assault at the Watch post. Jon Snow was given the duty of executing her, in the end he could not bring himself to complete his task and foolishly allowed her to escape. He recaptures her and in doing so manages to lose his way from the rest of the Night's Watchmen. Having found himself lost in the middle North of The Wall, Ygritte leads him to an ambush with the Wildling. In an attempt to save his life and honor the wishes of Qhorin Halfhand, Jon becomes a spy within the Wildling forces. He convinces the Wildlings that he was a traitor in Night's Watch and wants to be a free man.
In Season 3, Jon Snow and Ygritte spend a large amount of time together as the Wildling forces plan to attack Castle Black, resulting in a romantic partnership. Ygritte proclaims her love for him after they made love in a cave, saying she wishes they could stay in this cave forever. In the end of Season 3, Ygritte realizes that Jon is still very much loyal to The Night's Watch after having failed to kill an innocent horse breeder. Soon after the Wildlings set to kill Jon Snow, while restraining Ygritte in order to block her from aiding Jon. As the fight commences Jon the victor, escapes on horse back without Ygritte. Away from the horse farm, Jon is confronted by Ygritte. Angry and brokenhearted she shoots several arrows into him and he desperately rides back to Castle Black safely.
In Season 4, Jon has fully recovered from his wounds and reported to his superiors that the Wildlings plan to attack Castle Black with an army lead by Mance Ryder. With their army marching south and Tormund's group ravaging villages on south of the Wall, it appears the Night's Watch will be smashed by both sides by its enemies. The only reason they haven't attacked is because Jon gave false intel to the Wildlings saying that a thousand man are staning guard on Castle Black, when actually a hundred are. When they are warned of the mutineers from Commander Mormont's group that have taken refuge in Craster's Keep, Jon proposes a mission to kill the mutineers and silencing before they could be found by Mance's army and forced to reveal the Watch's true number. While, the mission turned out to be successful, in the next full moon the vast Wildling army reaches the Wall. A battle ensues which Jon takes control of the Watch after its commanders become unavailable or too injured to keep orders, and despite the massive onslaught from both sides, the Watch is successful. Unfortunately during the fighting, Ygritte is killed by a stray arrow and dies on Jon's arms.
The following morning, Jon discusses with Sam his suicidal solution to end the wildling threat: he plans to assassinate Mance Rayder, noting that he is the only thing binding the disparate wildling clans that make up the army, and his death will rob them of that purpose and leadership. Jon finds Mance in a wildling camp north of the Wall and claims he wants to negotiate with him. quickly deduces that Jon came to parley with Mance simply so he could assassinate him. Before anyone can make a move, they are interrupted by Stannis Baratheon and his army, who quickly subdue the Wildling menace.