Hypnos is the personification of sleep and Thanatos 's twin brother. Hypnos is a son of Nyx, primordial goddess of the night and Erebus, personification of darkness. Hypnos is the brother of Aether, Hemera, Thanatos, the Fates, the Keres, the Oneiroi, the Hesperides and many others. Hypnos is the husband of Pasithea, youngest of the Graces, daughters of Zeus and Eurynome. Ovid names him the father of the Oneiroi, gods of dreams. Hypnos lives in Tartarus with his mother Nyx and his siblings such as the Oneiroi, the Fates, Thanatos, Hecate, Hemera and others.