In the long ago, human women bore the children of angels, and something shining in the blood of those children's children carried on through the generations: Tom Whitshire was one of these children, and Holly Beckett, Keisha Talley and Marcia Carey; Deanna Connell and Samuel Campbell both, Caroline Macgregor and Eric Winchester, and the daughter of Deanna and Samuel and the son of Caroline and Eric both shone the more brightly for it; these bloodlines tend to only children, so Mary and John were all the more precious for their rarity. One in one thousand, two in ten thousand, says the Gospel of Thomas, but that was written by someone who was sure there were no more than five thousand people in all the world—the children of Mary Campbell and John Winchester were born the only two in ten billion with the names of the strongest archangels written in their blood. Azazel may have tainted the younger one, creating that crack through which Lucifer might yet gain entry, but in the end it won't matter, because Sam and Dean are Winchesters and Campbells and that means more than just the power in their blood, and the same prophet who anticipated their birth (two in all the world) said that these two will stand as a single one.