Heidegger's Bible Handbook: Philemon: Inscription
1. The Epistle is inscribed to Philemon, a Phrygian, a Gentile.
This Epistle was written by Saint Paul πρὸς Φιλήμονα, to Philemon. Whom Theophylact makes a Phrygian with respect to race; Jerome, a Colossian with respect native city; but others, a Laodicean. That he was not a Jew, but a Gentile, some gather from this, that Onesimus a Gentile, verse 16, is called ἀδελφὸν καὶ ἐν σαρκὶ καὶ ἐν Κυρίῳ, a brother, both in the flesh and in the Lord.