Hypnos
Parents: Nox (Night) and Erebrus (Darkness).
Children: Morpheus (dreams)
Spouse: Pasithea (one of the younger Graces) Hera gives Pasithea to Hypnos in marriage in exchange for putting Zeus to sleep in Mount Ida so that Hera can crush the Trojens while he sleeps.
Important Relatives: His brother, Thanatos (death).
Appearance: A winged youth.
Function: Hypnos is sleep incarnate.
Thanatos
Parents: Nox (night) and Erebrus (darkness).
Children: None.
Spouse: None.
Important Relatives: His brother, Hypnos, and his nephew Morpheus.
Appearance: A winged youth, like his brother Hypnos. He is also portrayed as a man robed in black with a sharp sword.
Function: Thanatos is Death incarnate. He naturally supplies Hades with his subjects, and plays a valuable role in the Underworld. Hermes, Persephone, and Iris also play a similar role (escorting the dead to the Underworld), but Thanatos is death.
Stories: Thanatos appears often in the story of Sisyphus where he is tied up by Sisyphus. While he is so engaged, no one can die. (this naturally makes Hades very angry. In some stories Hades, rather than Thanatos, is chained) In some versions of the story of Alcetis, Thanatos is wrestled by Hercules for the life of Alcetis.
Documents: Thanatos
Morpheus
Parents: Hypnos and Pasithea
Children: None.
Spouse: None.
Important Relatives: His father Hypnos and his uncle, Thanatos.
Appearance: A winged youth.
Function: Morpheus causes dreams.