Achaeus (flourished 3rd century BC) was a Greek Macedonian nobleman and was the second son born to King and founder of the Seleucid Empire Seleucus I Nicator and Persian noblewoman Apama. Achaeus was of Greek and Persian descent. His sisters were Apama and Laodice, while his brother was the second Seleucid King Antiochus I Soter. Achaeus is sometimes called Achaeus the Elder to distinguish himself from his grandson of the same name.

Achaeus was a wealthy man and owned estates in Anatolia. Achaeus was a benefactor for those who assisted during the war against the Galatians. The Seleucid military campaign against the Galatians took place between 269 BC-267 BC, during the reign of Antiochus I. Those who had assisted Antiochus I and Achaeus were taken prisoner and Achaeus paid for their ransom to be released. Antiochus I won this military campaign. Those who had Acheaus as their benefactor inscribed their benefaction on a stone stele and placed it in the sanctuary of Zeus at Babakome and that of Apollo at Kiddioukome. The descendants of those who were saved by Achaeus for all time were granted a seat of honor at the public festivals and sacrificed to Achaeus every year an ox in the sanctuary of Zeus.

Achaeus married an unnamed Greek woman, probably a relation of the Diadochi. From this marriage, he two sons and two daughters:

   * Alexander

   * Andromachus, a general. He was the father of Achaeus (general) and Laodice II mother of the Seleucid King Antiochus III the Great.

   * Laodice I, a Seleucid Queen who married her paternal cousin Seleucid King Antiochus II Theos, hence was the mother of another Seleucid King Seleucus II Callinicus.

   * Antiochis, who married a Greek nobleman called Attalus and was the mother of King Attalus I of Pergamon.

Achaeus

Achaeus (Ancient Greek: Ἀχαιός; flourished 3rd century BC) was a Greek Macedonian nobleman and was the second son born to King and founder of the Seleucid Empire Seleucus I Nicator and Persian noblewoman Apama I. Achaeus was of Greek and Persian descent. He had three siblings: one brother the Seleucid King Antiochus I Soter and two sisters: Apama and Laodice. Achaeus is sometimes called Achaeus the Elder, to distinguish him from his grandson the Seleucid General, Achaeus.

Achaeus was a wealthy man and owned estates in Anatolia. Achaeus was a benefactor for those who assisted during the war against the Galatians. The Seleucid military campaign against the Galatians took place between 269 BC-267 BC, during the reign of Antiochus I. Those who had assisted Antiochus I and Achaeus were taken prisoner and Achaeus paid for their ransom to be released. Antiochus I won this military campaign. Those who had Achaeus as their benefactor inscribed their benefaction on a stone stele and placed it in the sanctuary of Zeus at Babakome and that of Apollo at Kiddioukome. The descendants of those who were saved by Achaeus for all time were granted a seat of honor at the public festivals and sacrificed to Achaeus every year an ox in the sanctuary of Zeus.

Achaeus married an unnamed Greek woman. From his wife, she had born him four children who were:

1. Antiochis, she married Attalus and became the mother of Attalus I, King of Pergamon.
2. Alexander, held high positions under his paternal uncle Antiochus I Soter.
3. Laodice I, she was the first wife of the Seleucid King Antiochus II Theos.
4. Andromachus, he was held captive by the Egyptian Pharaoh Ptolemy III Euergetes.

Source :

https://en.wikipedia.org/wiki/Achaeus_(son_of_Seleucus_I_Nicator)