1)
What is the significance of the five sons of Midyan - 'Eifah Eifer, Chanoch, Avida and Elda'ah' listed here?
1.
Rashi (to Bamidbar 25:16): They became the five tribes of Midyan mentioned there. The king of the third tribe was Tzur (the father of Kozbi).
2)
Why does it say, "Kol Eleh Bnei Keturah"?
1.
Malbim: This teaches that their lineage does not follow Avraham.
