Quoting Commentary for I Kings 7:51

AND, BEHOLD, A CARAVAN OF ISHMAELITES CAME FROM GILEAD. When they looked up and saw at a distance men approaching from the direction of Gilead,⁷⁶Ramban’s intent is to explain why Scripture refers to these men first as Ishmaelites, then as Midianites (Verse 28), and again as Ishmaelites (ibid.), and finally as Midianites (Verse 36). they recognized them as a camel caravan of Ishmaelites on their way to Egypt, for it was from Gilead that balms and spices came, and it was their custom to bring it to Egypt. This was why Judah said to them, “Behold these men come from afar and are travelling to a distant country. Let us sell him to them so that the matter should not become known.” And when they came near they discovered them to be merchants of spices and balms — Midianites, merchantmen⁷⁷Verse 28 here. — who had hired the camels from the Ishmaelites. They sold Joseph to the Midianites who purchased him for profit, but the company of Ishmaelites, the lessors of the camels, would not purchase him for their own investment purposes. The verse which states, And they sold Joseph to the Ishmaelites,⁷⁷Verse 28 here. means that it was to them that the Midianites who bought him turned him over, for they were the ones who transported the merchandise to Egypt. This is also the meaning of the verse, From the hand of the Ishmaelites, that had brought him down thither,⁷⁸39:1. for he was in their care. But the Midianites were his masters, and they made trade with him. This is the sense of the verse, And the Midianites sold him to Egypt.⁷⁹Verse 36 here.
All stories in Scripture are written in this manner: sometimes it is told in the name of the authority who commands that it be done, and other times in the name of the agent who performs the act. Such a case is the verse, All the great work of the Eternal which He did,⁸⁰Deuteronomy 11:7. while elsewhere it states, Which Moses did in the sight of all Israel.⁸¹Ibid., 34:12. Similarly it says, Thus all the work that king Solomon did in the house of the Eternal was finished,⁸²I Kings 7:51. but it was Hiram that did it, as it is written, And he came to king Solomon, and wrought all his work.⁸³Ibid., Verse 14. In the case of Joseph himself, the verse says, And whatsoever they did there, he was the doer of it,⁸⁴Further, 39:22. thus ascribing the action both to he who commanded it and the one who did it.
Rabbi Abraham ibn Ezra says that the Midianites are called Ishmaelites, just as Scripture, in speaking of Midianite kings, says, Because they were Ishmaelites.⁸⁵Judges 8:24. But the matter is not as Ibn Ezra considered it to be since the verse which states, For they had golden ear-rings, because they were Ishmaelites,⁸⁵Judges 8:24. alludes to “the children of the east” whose war it was, as it is written, Now all the Midianites and Amalekites and the children of the east assembled themselves together,⁸⁶Ibid., 6:33. and “the children of the east” are Ishmaelites, for concerning all the sons of the concubines that Abraham had, it is said, And he sent them away from Isaac his son, while he yet lived, eastward, unto the east country.⁸⁷Above, 25:6. It is also possible that the kings were Ishmaelites who ruled over Midian. Otherwise, why should “kings of Midian”⁸⁸Judges 8:26. be called by the name of Ishmael their brother?
In line with the literal sense of Scripture the correct interpretation concerning the sale of Joseph is as we have said. But our Rabbis have said⁸⁹Bereshith Rabbah 84:2. that he was sold several times [and have thereby explained why his captors are alternately referred to as Midianites and Ishmaelites].