Two momentous events happened late in Game of Thrones season 6. First, Bran learned through his visions of the past that Jon Snow was not in fact his half-brother, but his cousin; not a bastard born of Ned Stark, but a (presumptive) bastard child of Rhaegar Targaryen and Lyanna Stark. Second, Jon Snow was crowned king in the North by the lords of the northern houses following his and Sansa’s military victory over Ramsay Bolton and, by proxy, the Lannisters. But they don’t know about his true heritage—and when they find out in Game of Thrones season 7, it could well be a big problem.

Why Jon Snow’s Birth May Jeopardize His New Crown

Although Jon Snow isn’t Ned’s trueborn son, the northern lords gave him the crown of the North thinking he was Ned’s son, both in blood and in spirit—even though Sansa contributed more to the victory. To them, he had proved he was worthy of the Stark name. They don’t know yet that he doesn’t actually have any of Ned’s blood in him, even if he does have some of the same spirit.

The Targaryens are not much loved by the Starks or the other northern lords. After all, Rhaegar kidnapping or running off with Lyanna led to the death of Ned’s father and older brother, and started Robert’s Rebellion besides. When the northern lords find out that Jon Snow is actually the grandson of the Mad King, their generous attitude to him is likely to change. And they will learn the truth, thanks to Howland Reed.

Jon Snow himself doesn’t even know how vulnerable his position is. The revelation of his heritage will come as just as large a surprise to Jon himself as to his new vassals. What will happen to Jon when he finds out? His ties to the North will remain strong, but he’ll suddenly realize he has a lot more in common with a woman he’s never met: Daenerys Targaryen, his aunt (and probably future wife). He may well need her help to maintain his new crown when the northern lords realize they’v succumbed once again, and by accident, to the blood of the dragon.