Which later wife of Abraham bore him Midian and five other sons?

Answer: Keturah

Abraham took another wife, Keturah, who bore him Zimran, Jokshan, Medan, Midian, Ishbak and Shuah.

“Now Abraham had taken another wife, named Keturah, and she bore him Zimran, Jokshan, Medan, Midian, Ishbak, and Shuah.”— Genesis 25:1-2 (BSB)