This week's coming finale of Game of Thrones Season 7 is entitled "The Dragon and The Wolf." Like the episode that had a similar name, "The Lion and The Rose," we assume this title means that "The Dragon" (House Targaryen) and "The Wolf" (House Stark) will be united in some manner, either by someone on their knees swearing fealty, or someone on their knees... doing other things. But before we join these two Houses in common cause, let us consider the history of the Starks and Targaryens.
Before we begin let us remember that though they are called the Seven Kingdoms, there are really nine. House Stark and House Targaryen are but two. House Stark has ruled the North, the largest land area in Westeros, from the Neck up, in some fashion, since the Age of Heroes and the last Long Night. House Targaryen, when it ruled in Westeros, did not have nearly that much land, instead only carving out the small eastern coast area known as the Crownlands.
But that didn't matter. House Targaryen's dragons meant that the lords of all the other areas, including the North bent the knee to them, and while their actual land holdings were small, Targaryen ruled all.
House Stark has ruled the North for so long, their line stretches back to the First Men, before the Wall was raised, in 8000 BC, during the Age of Heroes. Only House Lannister has a line that goes back that long.
Brandon the Builder founded the House, and built Winterfell, as well as designed and oversaw construction of the Wall and the Night's Watch castles therein. He styled House Stark "The Kings Of Winter," and promised to always have members of their family help staff the newly built Wall. Their house had offshoots, including the Greystarks and the Karstarks, who became bannermen to their leadership.
The 13th Lord Commander of the Night's Watch, which is the book's version of the Night's King. (Note the different spelling.)
The Starks held off the Andal Invasion in 6,000 AC, which is why the Faith of the Seven never spread North. They still worship the Old Gods as the Children of the Forest taught the First Men.
They also fought back several wildling invasions with the help of House Umber, fought with House Arryn over the Three Sisters Islands, before the Targaryens came. They even had a fleet that challenged the Ironborn. But when King Brandon the Shipwright died, his son burned the fleet in grief, and the Starks never sailed again.
The final King of Winter was Torrhen, the King Who Knelt. He bent the knee to Aegon I Targaryen, one of the first to do so. He got to keep the entire area as his Wardenship, and the Targaryens basically left them alone.
The only House that rivals Stark in having their history fleshed out. The Targaryens were late to the party, arriving on Westeros to conquer in 2BC, just over 110 years after the Doom of Valyria killed off every other Valyrian house and dragon in existence except theirs.
Prior to the Doom, the Targaryens had actually been a very small House in Valyrian society. They had only five dragons to their name when they left to go to Dragonstone, due to visions of the Doom had by Daenerys.
Things were different in Westeros. The Targaryens went from being a little dragon in a big chain of volcanoes to the big fish in a little pond. All they needed were three dragons and the entire continent was theirs... All except Dorne, whose ruling house had the blood of the ancient Valyria enemy, the Rhoynish.
The Dornish were conquered through intermarriage, the first family that the Targaryens allowed into their habit of breeding brother to sister to keep the blood of the dragon line pure. The Targaryens did start marrying their extra children into other Houses, notably engaging themselves to House Baratheon of the nearby Stormlands, and House Tyrell of the Reach.
Meanwhile, the Targaryens started keeping their dragons chained up to prevent them from roasting small children, and they began to dwindle in size and stature. At their peak, the Targaryens had fourteen dragons. But the civil war known as The Dance of Dragons decimated both their lineage and their dragons. The last one was never more than the size of a small dog and died in 153 AC.
As we know, the last 100 years of the Targaryen reign, the House began to lose their grip on the continent. Broken engagements to Houses Baratheon and Tully set those houses at odds with them during Aegon "Egg" Targaryen's reign. (Maester Aemon's younger brother.) They became obsessed with a prophecy of "The Prince That Was Promised," attempting to forge a line that would produce this mythical heir. Meanwhile, the other Houses all started intermarrying at the suggestion of the maesters, forging one large alliance against their dragon rulers.
Then, in 281 AC, the Year of the False Spring, Rhaegar Targaryen,and Lyanna Stark fell in love, with disastrous results. Robert's Rebellion succeeded, and the last living Targaryens, save one, were driven to Essos and hiding.
Never The Twain Shall Meet... Until Now
Save one: Jon Snow, Real Westerosi Hero™. Jon Snow is special, as we've learned, with Melisandre bringing him back from the dead and all that, and the vague suggestions it is he who is this fabled "Prince That Was Promised."
But there's a reason with Jon it might be true. Look back over those two histories, and what do you notice about them? Other than Torrhen bending the knee, the Starks and the Targaryens actually don't have very much to do with each other. Yes, the Starks sent troops to fight in the failed conquest of Dorne, they picked a side in the Dance of Dragons, but mostly stayed out of it.
Going down to King's Landing was generally regarded by Northerns as a bad move. In fact, the burning of Brandon and Rickon Stark by Aerys was one of the few times the Starks did so. And because of this, the Targaryens never really attempted to ever engage themselves to the Starks. If anything, they pushed the Starks and Arryns to intermarry to keep the areas from fighting each other, as they had been doing before the conquest.
Jon Snow isn't just special because the show says so, He's special because he is the first time the Targaryen and Starks have produced an heir that combines their blood lines. He is the blood of the dragon and the old blood of Westeros. If he does eventually sit the Iron Throne, his line will be the first to rule the entire continent that has been in Westeros since the beginning of time.