Read Numbers 26:21 Using Other Translations
And the sons of Pharez were; of Hezron, the family of the Hezronites: of Hamul, the family of the Hamulites.
And the sons of Perez were: of Hezron, the clan of the Hezronites; of Hamul, the clan of the Hamulites.
These were the subclans descended from the Perezites: The Hezronites, named after their ancestor Hezron. The Hamulites, named after their ancestor Hamul.