Tros (Ancient Greek: Τρώς) is the eponymous king from whom Troy and the Trojans take their name. Son of Erichthonius (by Astyoche daughter of Simoeis) — or, in some accounts, of Ilus I — he married Callirrhoe daughter of Scamander (or Acallaris daughter of Eumedes) and fathered Ilus, Assaracus, and Ganymede, the three branches of the Trojan royal house. When Zeus abducted Ganymede, Hermes brought Tros immortal horses as recompense. Distinct from the Iliadic warrior Tros son of Alastor (tros-alastorid).
Adapted from Wikipedia, "Tros (mythology)" · CC BY-SA 4.0
I.Genealogy
Homer's Aeneas speech (Iliad 20) traces Dardanus → Erichthonius → Tros, then Tros' three peerless sons Ilus, Assaracus, and godlike Ganymede. Apollodorus has Erichthonius marry Astyoche daughter of Simoeis and beget Tros, who names the country Troy and marries Callirrhoe daughter of Scamander; Dionysius of Halicarnassus instead makes Tros' mother Callirrhoe and his wife Acallaris. Daughters Cleopatra and Cleomestra are also named in some lists.
Ilus founds Ilios in the plain; Assaracus' line runs Capys → Anchises → Aeneas; Ganymede is taken to Olympus as cupbearer.
II.Ganymede and the horses
When Zeus carried off Ganymede, Tros grieved until Hermes assured him the boy was immortal and cupbearer to the gods, and gave him a pair of horses so swift they could run over water and standing grain — the stock later prized among the Trojans and stolen in part by Anchises for Aeneas' team (Iliad 5).
Homonym care: not tros-alastorid, the Lycian Alastor's son slain by Achilles in the Iliad.