Background
Kronos and Rhea had a total of six children, but when Kronos was told he would be dethroned by one of his children, after they were born he would swallow them whole so they would live in his stomach. However, Rhea wasn't happy about the situation, so when her sixth and last child was born, she gave Kronos a rock instead of Zeus and she smuggled him out to Cretes where he was raised by the Nymphs. Once he had grown up, he started communicating with Rhea and they made a plan to retrieve Zeus' brothers and sisters. Zeus made Kronos throw up, and all of his brothers ande sisters came out, and so did the rock. Together the siblings dethroned their father, and the brothers decided to split the world among them. Posiedon became the god of the skies, Hades became the god of the underworld and dead, and Posiedon became the god of the seas and oceans.
Family
Mother and father: Kronos and Rhea
Siblings: Hades, Posiedon, Demeter, Hera, and Hestia
Children:
Immortal-
Agdistis, Aigipan, Alatheia, Aphrodite, Apollon, Ares, Artemis, Asopos, Ate, Athene, Britomartis, Dike, Dionysos, Eilethyia, Eirene, Eris, Ersa, Eunomia, Harmonia, Hebe, Hephaistos, Hermes, Horai, Kabeiroi, Kairos, Litai, Melinoe, Moirai, Mousai, Nemea, Nymphai, Pan, Pandeia, Persephone, Phasis, Zagreos.
Mortal-
Aiakos, Aithlios, Akheilos, Alexandros, Amphion, Argas, Arkas, Arkeisios, Atymnios, Dardanos, Emathion, Endymion, Epaphos, Graikos, Helene, Hellen, Herakles(1), Herakles(2), Herophile, Iarbas, Iasion, Keroessa, Kolaxes, Korinthos, Krinakos, Kronios, Kytos, Lakedaimon, Latinos, Magnes, Makedon, Manes, Megaros, Meliteus, Minos, Myrmidon, Orion, Pelasgos, Peirithous, Perseus, Polyduekes, Rhadamanthys, Saon, Sarpedon(1), Sarpedon, Spartaios, Tantalos, Targitous, Tityos, Zethos.
Siblings: Hades, Posiedon, Demeter, Hera, and Hestia
Children:
Immortal-
Agdistis, Aigipan, Alatheia, Aphrodite, Apollon, Ares, Artemis, Asopos, Ate, Athene, Britomartis, Dike, Dionysos, Eilethyia, Eirene, Eris, Ersa, Eunomia, Harmonia, Hebe, Hephaistos, Hermes, Horai, Kabeiroi, Kairos, Litai, Melinoe, Moirai, Mousai, Nemea, Nymphai, Pan, Pandeia, Persephone, Phasis, Zagreos.
Mortal-
Aiakos, Aithlios, Akheilos, Alexandros, Amphion, Argas, Arkas, Arkeisios, Atymnios, Dardanos, Emathion, Endymion, Epaphos, Graikos, Helene, Hellen, Herakles(1), Herakles(2), Herophile, Iarbas, Iasion, Keroessa, Kolaxes, Korinthos, Krinakos, Kronios, Kytos, Lakedaimon, Latinos, Magnes, Makedon, Manes, Megaros, Meliteus, Minos, Myrmidon, Orion, Pelasgos, Peirithous, Perseus, Polyduekes, Rhadamanthys, Saon, Sarpedon(1), Sarpedon, Spartaios, Tantalos, Targitous, Tityos, Zethos.