Erebus, the personification of darkness had various children with his sister Nyx (Night). Aether, Hypnos, Thanatos, Hemera, Styx, Charon, Geras, the Hesperides and the Fates. Erebus ruled the place where the dead passed on after their death.
"Theogony" is a poem by Hesiod describing the origins of the Greek gods. In the beginning, Chaos existed in the entire universe then gave birth to Gaia (Earth), Eros (Love), Erebus (Darkness), Nyx (Night) and Tartarus (Underworld). The poem shows how the gods mated with each other to complete creation and from there where Greek mythology begins i.e. Zeus, Hera, Hades, Poseidon etc.