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).
Where is it written that Noah and his descendants were the only humans to have survived the flood? The order from God was to take two of every flesh aboard the Ark. Since the Bible is the record of the history of man as it pertains to the line from Adam to Christ. Of course there had to be other survivors, the intent was to drive the evil, and the evil doers from the Earth, not exterminate all but the Hebrew line. I would surmise logically, that on board the Ark were what we call Negroids, Whites, or any other race that existed. How else can you say that there are different “races” without them surviving? In the New Testament, Jesus actually says that the Kenites are the sons of Cain. Kenites are described in the Bible as such. The church of Philadelphia was praised because they taught that this “serpent seed” still existed. He will specifically punish those that say they are “Jews” but are NOT. They are of the synagogue of Satan. Kenites, look it up in a Bible that hasn’t been altered, use a Strongs Concordance, it does help.