Jon Snow is the mysterious bastard child of Ned Stark. The highly-honorable Stark brought Snow home with him to Winterfell after returning from the war to overthrown the Targaryens. Ned never reveals much about Snow's mother or why he brought him home after the war. Snow is a capable fighter and leader who is forced to follow a different lifepath than the rest of the Stark clan because of his ignoble birth.
Photo credit: HBO