Titans. In Greek mythology, the Titans were the pre-Olympian gods. According to the Theogony of Hesiod, they were the twelve children of the primordial parents Uranus and Gaia, with six male Titans: Oceanus, Coeus, Crius, Hyperion, Iapetus, and Cronus, and six female Titans, called the Titanides: Theia, Rhea, Themis, Mnemosyne, Phoebe, and Tethys. Cronus and his sister Rhea were the parents of the first generation of Olympians: Zeus and his five siblings Hestia, Demeter, Hera, Hades and Poseidon. Descendants of the Titans 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 told how Cronus seized power from his father Uranus, and ruled the cosmos with the Titans as his subordinates, and how Cronus and the Titans were in turn defeated and replaced as the ruling pantheon of gods, by Zeus and the Olympians, in a ten-year war called the Titanomachy. As a result of this war of the gods, Cronus and the vanquished Titans were banished from the upper world, being held imprisoned, under guard in Tartarus, although apparently, some of the Titans were allowed to remain free. 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 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, Selene, and Eos. From Iapetos 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, and the three Moirai, and Mnemosyne bore the nine Muses. While the descendants of the Titans Oceanus and Tethys, Cronus and Rhea, Themis, and Mnemosyne are not normally considered to be Titans, descendants of the other Titans, notably: Leto, Helios, Atlas and Prometheus, are themselves sometimes referred to as Titans.