The GENTILES were generally considered to be non-Jews [“GENTILES” – Greek: “ethnos” – heathen, people, and nations other than Israel]. From Adam to Abraham there were only GENTILES in the world. From Abraham to Christ there were believing Jews (righteous remnant – true Israelites) and Hebrews or Israel (not just Judah) and GENTILES in the world.
From Christ onward in human history there are only unbelievers and Christians (believing Jews and believing Gentiles) in the world. After AD 70 the unbelieving Jews and Gentiles are the same as far as God’s people are concerned. After the resurrection of Christ, the believing Gentiles were included with all believing Hebrews as the “True Jews,” people of God (the new nation of spiritual Israel).
“48 Now when the GENTILES heard this, they were glad and glorified the word of the Lord. And as many as had been appointed to eternal life believed.” (Acts 13:48).
“7 Therefore know that only those who are of faith are sons of Abraham. 8And the Scripture, foreseeing that God would justify the GENTILES by faith, preached the gospel to Abraham beforehand, saying, “In you all the nations shall be blessed.” (Gal. 3:7-8).
“26For you are ALL sons of God through FAITH IN CHRIST JESUS . 27For as many of you as were baptized into Christ have put on Christ. 28There is NEITHER JEW NOR GREEK (Gentiles), there is neither slave nor free, there is neither male nor female; for YOU ARE ALL ONE IN CHRIST JESUS. 29And if you are Christ’s, then you are Abraham’s seed, and HEIRS ACCORDING TO THE PROMISE.” (Gal. 3:26-29).
[For a more in-depth study see eschatology “Study Series 11 on Romans 11”]