The interesting characters are all the fruit of two parents, not one
The silent emptiness of this world was filled when Gaia bore two sons all on her own* The first was PONTUS, the sea, and the second was OURANOS, the sky — better known to us as Uranus, the sound of whose name has ever been the cause of great delight to children from nine to ninety.
* This trick of virgin birth, or parthenogenesis, can be found in nature still. In aphids, some lizards and even sharks it is a reasonably common way to have young. There won’t be the variation that two sets of genes allow; this is the same in the genesis of the Greek gods. The interesting ones are all the fruit of two parents, not one.
Fry, Stephen. 2017. Mythos: The Greek Myths Retold. London, England: Penguin. p. 5