In Greek mythology, the Titans (, hoi Tītânes, , ho Tītân) were the pre-Olympian gods. According to the Theogony of Hesiod, they were the twelve children of the primordial parents Uranus (Sky) and Gaia (Earth), with six male Titans—Oceanus, Coeus, Crius, Hyperion, Iapetus, and Cronus—and six female Titans, called the Titanides or "Titanesses" (, hai Tītānídes)—Theia, Rhea, Themis, Mnemosyne, Phoebe, and Tethys. Cronus mated with his older sister Rhea, who then bore the first generation of Olympians: the six siblings Zeus, Hades, Poseidon, Hestia, Demeter, and Hera. Certain descendants of the Titans, such as Prometheus, Helios, and Leto, are sometimes also called Titans. The Titans were the former gods: the generation of gods preceding the Olympians. They were overthrown as part of the Greek succession myth, which tells how Cronus seized power from his father Uranus and ruled the cosmos with his fellow Titans before being in turn defeated and replaced as the ruling pantheon of gods by Zeus and the Olympians in a ten-year war called "the Titanomachy" ( hē Tītānomakhíā). As a result of this war, the vanquished Titans were banished from the upper world and held imprisoned under guard in Tartarus, although apparently some Titans were allowed to remain free. Genealogy Hesiod's genealogy According to Hesiod, the Titan offspring of Uranus and Gaia were Oceanus, Coeus, Crius, Hyperion, Iapetus, Theia, Rhea, Themis, Mnemosyne, Phoebe, Tethys, and Cronus. Eight of the Titan brothers and sisters married each other: Oceanus and Tethys, Coeus and Phoebe, Hyperion and Theia, and Cronus and Rhea. The other two Titan brothers married outside their immediate family. Iapetus married his niece Clymene, the daughter of Oceanus and Tethys, while Crius married his half-sister Eurybia, the daughter of Gaia and Pontus. The two remaining Titan sisters, Themis and Mnemosyne, became wives of their nephew Zeus. From Oceanus and Tethys came the three thousand river gods, and three thousand Oceanid nymphs. From Coeus and Phoebe came Leto, another wife of Zeus, and Asteria. From Crius and Eurybia came Astraeus, Pallas, and Perses. From Hyperion and Theia came the celestial personifications Helios (Sun), Selene (Moon), and Eos (Dawn). From Iapetus and Clymene came Atlas, Menoetius, Prometheus, and Epimetheus. From Cronus and Rhea came the Olympians: Hestia, Demeter, Hera, Hades, Poseidon, and Zeus. By Zeus, Themis bore the three Horae (Hours), and the three Moirai (Fates), and Mnemosyne bore the nine Muses. While the descendants of the Titans