We are not finished with Esau and his descendants and the trouble they are going to be to Jacob’s side of the family. Esau had Eliphaz, by Adah his first wife, who had a concubine named Timna who had Amalek (Gen. 36:12). She is attributed to Adah (a true wife in the genealogy) but is listed last. For Timna see 1 Chronicles 1:36-39.
The Amalekites are cursed and the Israelites are to be fighting them from generation to generation because they attacked the Israel column (Exodus 17:8-15) as they headed to the Promised Land. Deuteronomy 25:17 – 19 is a serious statement to the Israelites about that incident; it is that commission that King Saul is trying to accomplish in I Samuel 14 and 15.
Josephus 2.1.2 assigns Amalek to the country of Idumea; this is where King Herod came from. Davis Dictionary of the Bible says the Idumeans had circumcision forced on them after being conquered by John Hyrcanus a Maccabaean ruler. This is why the Jews hated Herod so much, he was not a Jew and very possibly an Edomite and he could have even been an Amalekite.
A side thought on this – there was always some kind of contention within Abraham’s family; Ishmael and Esau did not seem like contented brothers and uncles but their genealogies made it into the Bible so that tells me that some communication did exist between parts of the family. Since Moses is credited with writing Genesis and parts of Esau’s history was definitely happening while they were in Egypt there was communication. Moses may have gotten some of the information while he was in Midian.
Other references to Esau/Edom/Amalek being destroyed or facing the judgment of God.