Achaeus, son of Xuthus

Achaeus
Eponymous of the Achaean race as well as their home, Achaea in Phthiotis
Abode	Athens, Lacedaemon, Achaea in Phthiotis
Personal Information
Children	Archander and Architeles
Parents	Xuthus and Creusa or Jupiter (Zeus) and Phthia
Siblings	Ion

In Greek mythology, Achaeus or Achaios (Ancient Greek: Ἀχαιός Akhaios derived from achos αχος  "grief, pain, woe") was, according to nearly all traditions, a son of Xuthus and Creusa, and consequently a brother of Ion and grandson of Hellen.Servius alone calls Achaeus a son of Jupiter (Zeus) and Pithia, probably a misspelling of Phthia, who was otherwise known as the daughter of Phoroneus compare the account of Clement. His children were Archander and Architeles.

The Achaeans regarded him as the author of their race, and derived from him their own name as well as that of Achaia, which was formerly called Aegialus. When his uncle Aeolus in Thessaly, whence he himself had come to Peloponnesus, died, he went there and made himself master of Phthiotis, which now also received from him the name of Achaia.

...
Wikipedia