His brethren had not many children. — His brethren, i.e., his fellow-tribesmen. The other Simeonite clans (Numbers 26:12), are meant.
Neither did all their family multiply. — Rather, nor did they multiply their whole clan. The word clan (mishpahath) is here used in the wider sense of tribe. This remark is borne out by what we otherwise know of the tribe of Simeon. It was never historically important, and appears to have ultimately been absorbed by Judah, within which its domain was included (Joshua 19:1). (Comp. Genesis 49:7 : “I will divide them in Jacob, and scatter them in Israel.”)