In vs. 28-42 there is a second series of tribes or peoples, derived from Abraham through Ishmael, Keturah’s sons, and Isaac. In the former series, the sons of Japheth and Ham were listed first, before the descendants of Shem. So now, the sons of Ishmael and of Keturah are given first, before those of Isaac are listed. Of Isaac’s sons, Esau precedes Israel, since the chronicler is leading up to Israel as the climax of his presentation.