The families of the Levites according to their fathers
That is, these were the heads of the families which sprang from them. And it is thought the following catalogue contains the successive heads or chiefs of their several families until the times of David, by whom they were distributed into several courses. Zimmah his son His grandson by his son Shimei, as appears from 1 Chronicles 6:42-43; the names of father and son being often used in Scripture of more remote progenitors or successors.