Edwin,
In Scripture, three classes of people are addressed: Jews, Gentiles, the Church. In the Gospels, the Church had not yet been founded, so two classes of people are dealt with: Jews and Gentiles. The Kingdom had been given to the Jews, but because they rejected it, and its King, it was given to the Gentiles; ie, Kingdom truths were revealed to them. When Christ returns, "all Israel will be saved," meaning the nation of Israel will be restored to its proper place within G-d's plan. For now, though, Israel's eyes are veiled to the truth, which is why Jesus spoke in parables--to show that what little knowledge they once had had been taken away from them--and which is why it is so difficult to win a Jew to Christ. It does happen, I am proof of that, but I say it is more difficult because our eyes are shut to the truth.
So in a sense you are correct, there are "two groups," but those two groups are divided along ethnic lines, Jew and Gentile.