1 Chronicles 6:48

These also are the generations of Aaron and Moses in the day that the LORD spake with Moses in mount Sinai. And these are the names of the sons of Aaron; Nadab the firstborn, and Abihu, Eleazar, and Ithamar. These are the names of the sons of Aaron, the priests which were anointed, whom he consecrated to minister in the priest's office. And Nadab and Abihu died before the LORD, when they offered strange fire before the LORD, in the wilderness of Sinai, and they had no children: and Eleazar and Ithamar ministered in the priest's office in the sight of Aaron their father. And the LORD spake unto Moses, saying, Bring the tribe of Levi near, and present them before Aaron the priest, that they may minister unto him. And they shall keep his charge, and the charge of the whole congregation before the tabernacle of the congregation, to do the service of the tabernacle. And they shall keep all the instruments of the tabernacle of the congregation, and the charge of the children of Israel, to do the service of the tabernacle. And thou shalt give the Levites unto Aaron and to his sons: they are wholly given unto him out of the children of Israel. And thou shalt appoint Aaron and his sons, and they shall wait on their priest's office: and the stranger that cometh nigh shall be put to death. And the LORD spake unto Moses, saying, And I, behold, I have taken the Levites from among the children of Israel instead of all the firstborn that openeth the matrix among the children of Israel: therefore the Levites shall be mine; Because all the firstborn are mine; for on the day that I smote all the firstborn in the land of Egypt I hallowed unto me all the firstborn in Israel, both man and beast: mine shall they be: I am the LORD. And the LORD spake unto Moses in the wilderness of Sinai, saying, Number the children of Levi after the house of their fathers, by their families: every male from a month old and upward shalt thou number them. And Moses numbered them according to the word of the LORD, as he was commanded. And these were the sons of Levi by their names; Gershon, and Kohath, and Merari. And these are the names of the sons of Gershon by their families; Libni, and Shimei. And the sons of Kohath by their families; Amram, and Izehar, Hebron, and Uzziel. And the sons of Merari by their families; Mahli, and Mushi. These are the families of the Levites according to the house of their fathers. Of Gershon was the family of the Libnites, and the family of the Shimites: these are the families of the Gershonites. Those that were numbered of them, according to the number of all the males, from a month old and upward, even those that were numbered of them were seven thousand and five hundred. The families of the Gershonites shall pitch behind the tabernacle westward. And the chief of the house of the father of the Gershonites shall be Eliasaph the son of Lael. And the charge of the sons of Gershon in the tabernacle of the congregation shall be the tabernacle, and the tent, the covering thereof, and the hanging for the door of the tabernacle of the congregation, And the hangings of the court, and the curtain for the door of the court, which is by the tabernacle, and by the altar round about, and the cords of it for all the service thereof. And of Kohath was the family of the Amramites, and the family of the Izeharites, and the family of the Hebronites, and the family of the Uzzielites: these are the families of the Kohathites. In the number of all the males, from a month old and upward, were eight thousand and six hundred, keeping the charge of the sanctuary. The families of the sons of Kohath shall pitch on the side of the tabernacle southward. And the chief of the house of the father of the families of the Kohathites shall be Elizaphan the son of Uzziel. And their charge shall be the ark, and the table, and the candlestick, and the altars, and the vessels of the sanctuary wherewith they minister, and the hanging, and all the service thereof. And Eleazar the son of Aaron the priest shall be chief over the chief of the Levites, and have the oversight of them that keep the charge of the sanctuary.

And he gathered together all the princes of Israel, with the priests and the Levites. Now the Levites were numbered from the age of thirty years and upward: and their number by their polls, man by man, was thirty and eight thousand. Of which, twenty and four thousand were to set forward the work of the house of the LORD; and six thousand were officers and judges: Moreover four thousand were porters; and four thousand praised the LORD with the instruments which I made, said David, to praise therewith. And David divided them into courses among the sons of Levi, namely, Gershon, Kohath, and Merari. Of the Gershonites were, Laadan, and Shimei. The sons of Laadan; the chief was Jehiel, and Zetham, and Joel, three. The sons of Shimei; Shelomith, and Haziel, and Haran, three. These were the chief of the fathers of Laadan. And the sons of Shimei were, Jahath, Zina, and Jeush, and Beriah. These four were the sons of Shimei. And Jahath was the chief, and Zizah the second: but Jeush and Beriah had not many sons; therefore they were in one reckoning, according to their father's house. The sons of Kohath; Amram, Izhar, Hebron, and Uzziel, four. The sons of Amram; Aaron and Moses: and Aaron was separated, that he should sanctify the most holy things, he and his sons for ever, to burn incense before the LORD, to minister unto him, and to bless in his name for ever. Now concerning Moses the man of God, his sons were named of the tribe of Levi. The sons of Moses were, Gershom, and Eliezer. Of the sons of Gershom, Shebuel was the chief. And the sons of Eliezer were, Rehabiah the chief. And Eliezer had none other sons; but the sons of Rehabiah were very many. Of the sons of Izhar; Shelomith the chief. Of the sons of Hebron; Jeriah the first, Amariah the second, Jahaziel the third, and Jekameam the fourth. Of the sons of Uzziel; Micah the first and Jesiah the second. The sons of Merari; Mahli, and Mushi. The sons of Mahli; Eleazar, and Kish. And Eleazar died, and had no sons, but daughters: and their brethren the sons of Kish took them. The sons of Mushi; Mahli, and Eder, and Jeremoth, three. These were the sons of Levi after the house of their fathers; even the chief of the fathers, as they were counted by number of names by their polls, that did the work for the service of the house of the LORD, from the age of twenty years and upward. For David said, The LORD God of Israel hath given rest unto his people, that they may dwell in Jerusalem for ever: And also unto the Levites; they shall no more carry the tabernacle, nor any vessels of it for the service thereof. For by the last words of David the Levites were numbered from twenty years old and above: Because their office was to wait on the sons of Aaron for the service of the house of the LORD, in the courts, and in the chambers, and in the purifying of all holy things, and the work of the service of the house of God; Both for the shewbread, and for the fine flour for meat offering, and for the unleavened cakes, and for that which is baked in the pan, and for that which is fried, and for all manner of measure and size; And to stand every morning to thank and praise the LORD, and likewise at even: And to offer all burnt sacrifices unto the LORD in the sabbaths, in the new moons, and on the set feasts, by number, according to the order commanded unto them, continually before the LORD: And that they should keep the charge of the tabernacle of the congregation, and the charge of the holy place, and the charge of the sons of Aaron their brethren, in the service of the house of the LORD.

The four and twentieth to Romamtiezer, he, his sons, and his brethren, were twelve.