In the Homer's Iliad and Odyssey the sun god is called Helios Hyperion, 'Sun High-one'. But in the Odyssey, Hesiod's Theogony and the Homeric Hymn to Demeter the sun is once in each work called Hyperonides 'son of Hyperion' and Hesiod certainly imagines Hyperion as a separate being in other places.
In later Greek literature Hyperion is always distinguished from Helios as a Titan, the son of Gaia 'Earth' and Uranus 'Sky' and the father of Helios 'Sun', Selene 'Moon' and Eos 'Dawn' by his sister Theia or, in the Homeric Hymn to Helios, Euryphaessa:
"Theia yielded to Hyperion's love and gave birth
to great Helios and bright Selene and Eos,
who brings light to all the mortals of this earth
and to the immortal gods who rule the wide sky."
(Hesiod, Theogony, 371-374)
Hyperion plays virtually no role in Greek cult and little role in mythology, save in lists of the twelve Titans. Later Greeks intellectualized their myths:
"Of Hyperion we are told that he was the first to understand, by diligent attention and observation, the movement of both the sun and the moon and the other stars, and the seasons as well, in that they are caused by these bodies, and to make these facts known to others; and that for this reason he was called the father of these bodies, since he had begotten, so to speak, the speculation about them and their nature.” Diodorus Siculus (5.67.1)