the Tale of Aquarius, aka Ganymede
When Ganymede’s father, King Tros of Troy or Laomedon, found out about Ganymede’s disappearance, he grieved so hard that Zeus sent Hermes on his behalf to give Tros or Laomedon two storm footed horses. In other accounts, Zeus gave Tros a golden vine and two swift horses that could run over water. Hermes was also ordered to assure the bereaved father that Ganymede was and would be immortal. Later, Heracles asked for the two beautiful horses in exchange for destroying the sea monster sent by Poseidon to besiege the city of Troy. Tros agreed and Heracles became the owner of the bribe sent by Zeus to Tros.
Upon hearing that Ganymede was to be cup bearer as well as Zeus’ lover, the infinitely jealous Hera was outraged. Therefor Zeus set Ganymede’s image among the stars as the constellation Aquarius, the water carrier"
--by Mia Gibson--
Source: Encyclopedia Mythica - Ganymede