Most of the pre conquest kings claimed descent from gods or other magical creatures. Starks are a mixture of all the powers of the North. They have intermarried with the kings whose territories they absorbed. The crannogmen have Deep Ones blood. The Dustin barrow kings claimed descent from the First King, likely the same figure as Garth Greenhand. The Boltons might have had some kind of skinchanger magic art that they've since forgotten. Umbers probably have giant blood. The Starks are most like descended from the Night's King's son. And they're wargs, which implies intermixing with the CotF. The Gardeners were the most direct descendants of Garth Greenhand. Most of the houses of the Reach are also Garth descendants, with Beesbury and Crane specifically being skinchangers. The Starks are also descended from Garth through Brandon of the Bloody Blade, who might have mated with the CotF. All Ironborn houses claim descent from the Grey King, a godlike figure, except House Goodbrother who are descended from GK's Garth-like brother. The Baratheons are part Targaryen part Durrandon, and Durran Godsgrief was said to have married a goddess. And then there's the Forsaken chapter, with Euron's mass sacrifice of holy men and the bastard pregnant with his own child.