במדבר, פרק כ״ו, פסוק כ׳

The census of the tribe of Judah traces the lineage of its people back to their founding ancestors. The counting process organized the tribe into distinct family groups, with each group taking its name from one of the original sons. The descendants of Shelah formed one family, and the descendants of Zerah formed another [ביאור שטיינזלץ].

The family line of Perez, however, experienced a much broader expansion. Instead of remaining a single group, his descendants separated into three distinct families. One group kept his name, while the other two branched out and were named after his own descendants, Hezron and Hamul [חזקוני].