The sons of King Mosiah II were Ammon, Aaron, Omner, Himni. Along with Alma the Younger, these four were initially numbered among the unbelievers and perpetrated crimes against the Church. Through the intercession of an angel of God, they, along with Alma, were turned from their evil ways and became powerful forces for good in the kingdom of God. The sons of Mosiah served a fourteen-year mission among the Lamanites in the time frame of around 90 BC to 77 BC, during which they brought thousands unto the Lord.
Now these sons of Mosiah were with Alma at the time the angel first appeared unto him; therefore Alma did rejoice exceedingly to see his brethren; and what added more to his joy, they were still his brethren in the Lord; yea, and they had waxed strong in the knowledge of the truth; for they were men of a sound understanding and they had searched the scriptures diligently, that they might know the word of God.
But this is not all; they had given themselves to much prayer, and fasting; therefore they had the spirit of prophecy, and the spirit of revelation, and when they taught, they taught with power and authority of God (Alma 17:2–3; see also the separate entries for Ammon, Aaron, Omner, and Himni).