Genesis 25:4

And the sons of Midian; Ephah, and Epher, and Hanoch, and Abidah, and Eldaah. All these were the children of Keturah.

The five named here — Ephah, Epher, Hanoch, Abidah, and Eldaah — are the sons of Midian and are counted as the children of Keturah by her union with Abraham, marking them as Abraham's descendants through Keturah. They belong to the descendants born from that later union, distinct as a line from the descendants of Isaac and Jacob. The verse stands in the continuing story of Abraham and his family, tracing Abraham's gradual development of faith and leading forward into the account of Isaac and his two sons with their defects and finally to Jacob's victory that made him Israel, prevailer with God.

Through Keturah Abraham's immediate family grew into a large circle of relatives, clans, sub-tribes and tribes, some of whom became nations of considerable repute. Having many sons in this way gave strength and protection, because in patriarchal life outside walled cities the family is the real unit for defense. Related families unite against a common foe even while quarreling among themselves, and nearness of relationship determines friendliness in time of need. The household so enlarged also illustrates Oriental polygamy in practice and the different esteem in which different wives were held.

The children of Abraham's later life through Keturah are distinguished from the one promised, special, elected line, for the inheritance promise belongs to Abraham's seed through Isaac, not to these other descendants. The posterity listed through Keturah was not the chosen line of the promise, but is set apart from the special, elected posterity to whom the promise referred. Abraham's other lines of descent through Keturah are therefore not included in the promises to Israel merely because they descend from Abraham, so that ancestry alone does not determine who is entitled to those promises.