According to Greek mythology, Hypnos (=Sleep) and Thanatos (=Death) were twin brothers and children of Night and Erebus (=darkness). Sleep was very much worshiped in mainland Greece. Epidaurus, Troizina and Olympia were important centers of sleep worship.
The children of sleep were Dreams (the Three Dreams), Morpheus, Phobitor (=phobia, fear) and Fantasus. They considered him a quiet and gentle god.
Hypnos and Hera
Hypnos on Homer, was living in Lemnos and there, with the help of Hera, took as his wife Pasithea, the goddess of rest. The legend states that Hera, who wanted to seduce Zeus to influence the Trojan war herself, went to Lemnos, met Hypnos and, after pleading with him “as the king of all the gods of all people”, promised him to give him as wife Pasithea, but on the condition that Hypnos would keep Zeus asleep for a while. Finally, after being convinced by Hera, Hypnos did as she said.
see also; The 147 orders of the Oracle of Delphi
There are many works of artists starring Hypnos, but also his brother, Death. Usually, Hypnos was imagined young with wings on its shoulders.