Targum Jonathan on Genesis
The sons of Jehuda, Er, Onan, Shelah, Pherets, and Zarach. But Er and Onan died, on account of their evil work in the land of Kenaan; and Shelah and Zarach had no children in the land of Kenaan; but the sons of Pherets who went down to Mizraim were Hetsron and Chamul.