Jon may be the brother of the Starks, but he isn't actually one of them. That surname, the sign of a Northern bastard, ensures that. Stannis even offered him the chance to become a fully-fledged Stark, but he refused on account of his vows to the Night's Watch. However, while those words may have previously kept him from holding any lands or titles, he's died and came back. Just a hunch, but there probably isn't any precedent for that in the Night's Watch handbook. There's a good chance that this serves as a loophole, allowing him to forsake those vows, which leads to him riding into battle with the Boltons. If he's victorious, which you'd imagine will be the case, then does that mean we're going to see him become Jon Stark, Warden of the North?