The sons of Midian were Ephah, Epher, Hanoch, Abida, and Eldaah. All these were descendants of Keturah.
Jewish Publication Society of America Version (JPS1917) - Genesis 25:4 >And the sons of Midian: Ephah, and Epher, and Hanoch, and Abida, and Eldaah. All these were the children of Keturah.