Jahath was the oldest son and Ziza was the second son. But Jeush and Beriah did not have many children. So Jeush and Beriah were counted like one family.
Shimei had four sons. They were Jahath, Ziza, Jeush, and Beriah.
Kohath had four sons. They were Amram, Izhar, Hebron, and Uzziel.