Was Moses's father-in-law Jethro descendant of Ishmael?

Jethro, Moses's father-in-law, is traditionally identified as a Midianite priest. The Midianites were descendants of Midian, who was a son of Abraham and Keturah, not Ishmael. While both Ishmael and Midian were descendants of Abraham, they belong to different genealogical lines, so Jethro is not considered a descendant of Ishmael.