See commentary on 3 Nephi 14:1-5. The Nephite Twelve along with Jesus’ original Twelve, probably coupled with all who have held keys of the priesthood, will be involved in judging the righteous of the house of Israel.
As “judges in Israel” they will be voices of advocacy for those who have lived the gospel, borne the cross of Christ in their daily lives, and endured in faith to the end. “The reality is that there will be a whole hierarchy of judges who, under Christ, shall judge the righteous,” wrote Elder Bruce R. McConkie. “He alone shall issue the decrees of damnation for the wicked.’ (Millennial Messiah, p. 520; see also Matthew 19:28; Revelation 20:4; D&C 29:12.)
How these Nephite Twelve and all the others will be involved in the judging of the righteous has not been fully revealed.”