There are three Hours ... Eunomia (Harmony), Dike (Justice) and Eirene (Peace).
The Hours (Horae) assist the Olympians by organizing the Seasons and adding balance to Nature.
Their personal relations to the other Immortals are only partially revealed. In The Iliad we see them personally attending Hera and her horses. They open the sky as Hera zooms from her home on Mount Olympos (Olympus) to Mount Ida to distract Zeus from the battle for Troy. (Iliad, book 5, line 749)
The Hours guard Mount Olympos with a dark veil and open and close the gates of the sky for the Immortals as they travel to and from their domains. Their charge is the vast sky and Mount Olympos.
The line numbers listed here correspond fairly well with the Lattimore and Murray/Wyatt translations of The Iliad. Other translations (Fitzgerald, Fagles et al) do not correspond as well but, with a small amount of effort, you should be able to find the reference you need regardless of the translation you use. Lattimore (ISBN 0226469409); A.T. Murray/William F. Wyatt Vol. I & II (ISBN 0674995791 and 0674995805); Robert Fitzgerald (ISBN 0374529051); Robert Fagles (ISBN 0140275363)