Ouranos

Ouranos (in Greek, Οὐρανός) is the Greek protogenos personifying the Sky. Ouranos', the Greek word for sky (a cognate of the English word air), Latinized form is Uranus. He is the husband of Gaea/Gaia alone. He was the first ruler of the universe until overthrown and castrated by his son, Kronos. Ouranos could be the greatest villain in Greek mythology, even being worse than Kronos but maybe not as bad as Gaia since she is his wife.

History
Ouranus and Gaea/Gaia were the gods of the sky and the Earth respectively. They became partners, and brought forth their children: the Cyclopes, the Hecatonchires and the Titans. When Ouranos saw his other children, he did not think they should not walk on the earth so he casted them into Tartarus and used Kampe as the jailer. Gaia was enraged with Ouranos and told Kronos to cut his father to pieces with a sickle, and he did so, making him the Lord of the the universe. But Kronos still did not free his brothers.

The Cyclopes
Arges

Brontes

Steropes

The Hundred-Handed Giants
Cottus

Briares

Gyges

The Titans
Oceanus

Koios

Krios

Hyperion

Iapetus

Theia

Rhea

Themis

Mnemosyne

Phoebe

Tethys

Kronos

Gods
Aphrodite

Ouranos didn't care for his children, in fact, he hated them. Most of all he hated his children that did not look normal, such as the Hecatonchires and Cyclopes. They were unsightly in his opinion, and he wanted them gone. But he couldn't kill them, because they were immortal.

So instead Ouranos threw the Hecatonchires and Cyclopes into Tartarus. This caused Gaea pain, and she was also furious because they were her children, and Ouranos cared nothing for them. She asked her children, the Titans, to get rid of Ouranos so she could save her other children, and only Kronos was brave enough to do it. He took a flint sickle Gaea made, and sliced his father into pieces. Nothing else was mentioned about Ouranus after that.

Kronos threw Ouranos's body into the ocean. Aphrodite, the goddess of love and beauty, was born from the foam. It is also said that Ouranos's ichor became The Furies.

Personality
Ouranus was a horrible father, and didn't care for his children. He was a terrible husband too, because it didn't hurt him that Gaea was so sad about the loss of her children.

The Titan's Curse
Ouranus doesn't appear in the books, but he is mentioned by the General, that a Titan must hold up the Sky because Ouranus is gone, and the Sky still longs to embrace the Earth. Atlas, a Titan, is assigned this torment as the First Olympian War.

The Heroes of Olympus
Though Ouranos hasn't made an appearance since his defeat at Kronos's hands, it is possible that he may reappear sometime in the series since Gaia is once again at large. However, he was hated by his wife and all living subjects during his rule, so chances are no one would actually want or try to resurrect him. He would be a powerful ally against Gaia, though.