New Revised Standard Version
The enrollment of the priests was according to their ancestral houses; that of the Levites from twenty years old and upwards was according to their offices, by their divisions.

Contemporary English Version
The priests were listed in the official records by clans, and the Levites 20 years old and older were listed by their duties.

New American Bible
The priests were inscribed in their family records according to their ancestral houses, as were the Levites twenty years of age and over according to their various offices and divisions.

Douay-Rheims Bible
To the priests by their families, and to the Levites from the twentieth year and upward, by their classes and companies.

To the priests by their families, and to the Levites from the twentieth year and upward, by their classes and companies.

genealogy

Numbers 3:15,20 Number the sons of Levi by the houses of their fathers and their families, every male from one month and upward. . . .

Numbers 4:38,42,46 The sons of Gerson also were numbered by the kindreds and houses of their fathers, . . .

Numbers 17:2,3 Speak to the children of Israel, and take of every one of them a rod by their kindreds, of all the princes of the tribes, twelve rods, and write the name of every man upon his rod. . . .

Ezra 2:59 And these are they that came up from Thelmela, Thelharsa, Cherub, and Adon, and Emer. And they could not shew the house of their fathers and their seed, whether they were of Israel.

twenty

Numbers 4:3 From thirty years old and upward, to fifty years old, of all that go in to stand and to minister in the tabernacle of the covenant.

Numbers 8:24 This is the law of the Levites: From twenty-five years old and upwards, they shall go in to minister in the tabernacle of the covenant.

1 Chronicles 23:24,27 These are the sons of Levi in their kindreds and families, princes by their courses, and the number of every head that did the works of the ministry of the house of the Lord from twenty years old and upward. . . .

by their courses

2 Chronicles 31:2 And Ezechias appointed companies of the priests, and the Levites, by their courses, every man in his own office, to wit, both of the priests, and of the Levites, for holocausts, and for peace offerings, to minister, and to praise, and to sing in the gates of the camp of the Lord.

1 Chronicles 24:20-31 Now of the rest of the sons of Levi, there was of the sons of Amram, Subael: and of the sons of Subael, Jehedeia. . . .

1 Chronicles 25:1-26:32 Moreover David and the chief officers of the army separated for the ministry the sons of Asaph, and of Heman, and of Idithun: to prophesy with harps, and with psalteries, and with cymbals according to their number serving in their appointed office. . . .