- Gaia & Uranus

Gaia, the goddess of Earth and daughter of Chaos, married Uranus, son of Ether and Day. He is the personification of the sky who ruled the universe. Both created the following children:

The Titans/Titaness, giants monsters.
The Giants, any of the large and powerful offspring of their parents who rebelled against the Olympian gods but were defeated in battle.
Oceanus, divinity of the stream believed to flow around the earth.
The Cyclopes, a race of Giants having a single eye in the middle of the forehead.
Hyperion, father of Helios (sun), Selene (moon), Eos (dawn).
Thetis, mother of Achilles by Peleus.
Rhea, a Titaness who is a fertility goddess.
Cronus, a Titan, god of the time.

Gaia gave birth also to a lot of monsters like Typheoeus during her relationship with Tartarus, an abyss under Hades where later the Titans were imprisoned. This monster had a hundred dragonheads, which spurted fire, and a bellowing many-tongued voice. He created the whirlwinds and fought with Zeus before the god hurled him beneath Mount Etna.