These men searched for their family records, but they could not find them and so were excluded from the priesthood as unclean.
KJV
These sought their register [among] those that were reckoned by genealogy, but it was not found: therefore were they, as polluted, put from the priesthood.
ASV
These sought their register among those that were reckoned by genealogy, but it was not found: therefore were they deemed polluted and put from the priesthood.