How are the Midianites related to Abraham and Israel?
The Midianites descended from Abraham through his second wife Keturah, since Midian was one of their sons. Though sharing Abraham's bloodline, they became archetypal enemies of Israel throughout antiquity, illustrating how Abraham's offspring included both covenant line and Israel's adversaries.
Les teaches that in Genesis 25, after Sarah had died, Abraham married Keturah when he was about 150 years old and had a bunch of sons by her. One of those sons was Midian, and from him came the Midianites, who were the arch enemies of Israel through their antiquities. Even so, these Midianites were sons of Abraham. Les points out that all the Middle Eastern families come from Abraham, except the original Egyptians, and that through Abraham's second marriage came more of Israel's mortal enemies. This shows the interrelation of Middle Eastern peoples and how Abraham's offspring included both the covenant line of Isaac and Jacob and Israel's adversaries.
And the sons of Midian; Ephah, and Epher, and Hanoch, and Abidah, and Eldaah. All these were the children of Keturah.