We start with the family records of Esau. We find that he was no more willing to stick with the one-man/one-woman ethic of creation than his brother was. This was an unfortunate development in history that honestly is indefensible. Esau takes his large family, his many wives, and relocates to the mountains of Seir. Tradition holds that his offspring, the Edomites, were some of the first inhabitants of the valley that has become the city of Petra.
A name worth noting in Esau's records is found in 36:4: Basemath, daughter of Ishmael, has a child named Reuel. that name will come back in Exodus 2:18. I would suggest that these are not the same Reuels, but that it becomes a family heritage name.
The remainder of the chapter traces the lineage of Esau into the times of the Edomites. Some of the exploits and events of their history are there, but it is obviously abbreviated, especially in comparison to the lives of Jacob and his offspring.
What, then, do we do with this? After all, the primary references to the Edomites in the Old Testament are to them as enemies (see Obadiah) and in the New Testament, Esau is one who lacked faith (Hebrews 12:16). We're not supposed to be Esau.
But the Bible is not merely a record of people that we should be like or not be like. The whole of Scripture is a testament to the faithfulness of God, to the glory of God. What do we gather here along those lines?
First, this reality: God selects some people and groups to work through specifically, as He did with Israel. However, that does not mean He is unaware or disconnected from everyone else.
Second, God's faithfulness is drawn from His character, not from anyone's worth or future worthiness. The family of Esau will not turn out fully God-honoring in their lives. God's promise to Abraham was still valid, no matter what would come. When God makes a promise, He keeps it.
Third, we see that God works through many avenues. While it's hard to be certain, the area that Esau's family, including Reuel, is toward the area where Keturah's offspring went as well. You would have the link between Reuel and the Midianites, and then you have the family that Moses flees to. A monotheistic family, servants of the One True God.
Moments like that are not coincidences. There are few coincidences in life--certainly none in the workings of the covenants of God.
Trust that God will work. Even if you cannot see how.