personification of sleep in Greek mythology

Hypnos is the god of sleep in Greek mythology. He is the son of Nyx and the twin brother of Thanatos, the god of death.

Hypnos and Thanathos on a Greek vase

His sons are the Oneroi: Morpheus, Phobetor and Phantasos.

His Roman equivalent was Somnus. Hypnos was represented as a gentle young man, usually with wings attached to his temples or shoulders.