Let’s see...
Dragonborn and Kobolds are Draconic, but neither is descended from Dragons. Rather, they are the children of Io.
Dragons are all the children of Tiamat, as are many other monsters both good and evil, and a lot of the gods. Truly ancient dragons can become true immortals, becoming something like a god. I’m toying with applying that to rare, blessed, Dragonborn and Kobolds, as well.
Bahamut is the champion of Io’s children in his father’s stead, and a patron of avengers.
Shadar-Kai and Vryloka are of one ancient race, older even than elves. Their home was a small group of islands similar in size to the British Isles. Their home was a nexus of power, connecting many leylines, and rich in natural resources (in my Eberron game I’ve added some stuff about dragon shards and prophecy marks), and so they came under attack.
Eventually, an attack was so great that their control over the mists couldn’t hold back the invaders, and their friendship with wolves and ravens and their martial prowess couldn’t withstand the onslaught. As the lesser islands were lost, the elders called upon the Three Sisters for a solution, willing to pay any price. The sisters were the most powerful of the people, and too young for such a burden. They begged the people to seek another way, but the elders demanded a permanent solution to hide the islands from outsiders and make it safe forever.
Finally, the sisters relented, admitting that their own battle power was not enough to save their home, and they called upon the power of the islands themselves, and they bound the people to themselves and to the islands, bound themselves to the spell and to their people, and sacrificed their own names to remove the name of their home from the minds of all, even the gods.
One third was bound to the black-haired sister, who became known as The Raven Queen, and became people of Shadow known as the Shadar-Kai.
One third was bound to the red-haired sister who became known as the Red Witch, and they became one with the wolf and gained the ability to become wolves, and are known as the Wolfblood Vryloka.
The final third was bound to the silver-haired sister who became known as the Lady of Silver Mist, and they gained power over the mists and the ability to become as the mist, and they are known as the Mistborn Vryloka.
Now, their ancient home is a myth, spoken of not by name but by epitaph, for the name is lost as surely as the true names of the people, and the three sisters.