Jacob and Esau

Hello Dear Rabbi, My question concerns the following. I always believed that the descendants of Ishamel are the Arab people. However, in just reading the passage Genesis, 25:23, in reference to Rebekah, "Two Nations are in thy womb, and two manner of people..." In reading this passage, one could make a (mistaken) conclusion that in fact, the descendants of Esau are the Arabs? And, if not, then who is the 2nd nation that is descended from Esau?

The descendants of Esau are listed in Genesis 36. One of them-Magdiel- is identified by Rashi with Rome.