King Jon Snow is the son of Lady Lyanna Stark and Rhaegar Targaryen, the Prince of Dragonstone. Since childhood, Jon is presented as the bastard son of Lord Eddard Stark, Lyanna's brother, and raised by Eddard alongside his legitimate children in Winterfell but his true parentage is kept a secret from everyone, including Jon himself.
In order to escape his bastard status, Jon joins the Night's Watch and is eventually chosen as Lord Commander. However, his decision to allow thousands of Free Folk safe passage through the wall alienates many of his black brethren, culminating in a riot where Jon is killed, but later revived by Melisandre.
Freed from his watch of the night's vows, Jon executes the mutineers and joins his cousin, Sansa Stark, in building an army to retake Winterfell from Bolton. After securing the help of some other Houses of the North and the Vale of Arryn, they successfully retake Ramsay Bolton Castle, restoring House Stark's rule over the North with Jon being declared the new King in the North by the lords. from North.