Were Naaman and Ard the sons or the grandsons of Benjamin?

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They were the sons of Benjamin

And the sons of Benjamin were Belah, and Becher, and Ashbel, Gera, and Naaman, Ehi, and Rosh, Muppim, and Huppim, and Ard. Genesis 46:21

They were the grandsons of Benjamin

And the sons of Bela were Ard and Naaman. Numbers 26:40