There is a wonderful reference in the Iliad of Homer to Ganymede's legend. According to this ancient epic, Ganymede was the son of Tros (who was a king of Troy). Because of his great beauty, the gods of Olympus selected Ganymede to be the mortal cup-bearer for Zeus:
handsomest of mortals, whom the gods
caught up to pour out drink for Zeus and live
amid immortals for his beauty's sake."
(Homer, Iliad, Book XX, 232-235)
The Iliad also indicates that Tros, Ganymede's father, received compensation for the loss of his son - he was given "under the Dawn and under Helios the finest horses in the world". These magnificent horses were indeed a princely ransom for a handsome prince.
There are, however, other versions of the story. One source claims that Zeus acted alone in abducting Ganymede. Either Zeus sent an eagle, or else assumed the form of an eagle himself, to carry the young man off to Olympus (incidentally, this dramatic scene of abduction was a favorite for artists over the centuries). It is said that Zeus immortalized Ganymede by making the handsome youth into the constellation Aquarius. And poetically, the water-carrier Aquarius is accompanied eternally in the night sky by Aquila (the eagle).
Who's Who in Classical Mythology