Who was the priest of Midian and father-in-law to Moses?

Jethro is recognized as the priest of Midian and the father-in-law of Moses. He plays a significant role in the narrative found in the Book of Exodus, particularly when he offers counsel to Moses on leadership and delegation, helping him to establish a more manageable system of governance among the Israelites. Jethro's status as a priest indicates his religious authority and the importance of his character in the broader context of Moses' story.

While Zipporah is Jethro's daughter and Moses’ wife, Gershom is their son, and Ruel is another name often associated with Jethro but not the primary name used in the Exodus account. Thus, Jethro stands out in this context as the correct answer, as his identity and relationship to Moses are explicitly detailed in the scripture.