Jethro was a “son of Abraham”. He lived among the Kenites, being as much a Kenite, as I am a Washingtonian. Proof is that he was a Priest of Midian, meaning he was of the line of Levi. Kenites are literally the sons of Cain. Not black, or white, just of the line of Cain, not of the line of Gods chosen people. If he was a descendant of Cain, Moses children would not be able to be priests.
For that to be correct, either Noah or his wife or one of the wives of his three sons must have been descended of Cain, as well as of Seth, who was Noah's recorded ancestor. (None of the wives is named in Scripture, so how would it be known from what ancestors they came?) It's interesting that Noah's father was named Lamech, which is also the name of one of the descendants of Cain who gets a few extra lines in the genealogy (on account of his two wives and his bad attitude). Kenites are not listed in Genesis 10 among the descendants of Noah.
The unique Levite priesthood was not established until after the Exodus, when the Levites supported Moses against the worshippers of the Golden Calf (Ex. 32:25-29).