Thanatos was the twin brother of Hypnos, the god of sleep. His parents were Nyx (night) and Erebos (darkness), and he had other siblings, including Geras (old age) and Nemesis, as well as Charon, the boatman who conducted souls across the River Styx to the underworld rules by Hades.
Thanatos killed by a gentle touch and the death he brought was natural and peaceful. This soft daimon of mortality is known by other names: Mors, Letus, Thanatus and Letum.
His sisters the Keres were the bringers of senseless or violent death. These harpies were associated with agony and hatred, murder, disease, battle. With their gnashing teeth, these gory beings also brought death by madness or famine.