Who was Merari?
Merari means "because of the anguish attending his birth" (Gen. 46:8,11). Third of Levi's sons, Gershon, Kohath, and Merari. Born before Jacob's going down to Egypt; of the 70 who accompanied him.
The Mahlites and Mushites were the two families of Merarites at the exodus and in the wilderness (1 Chr. 6:19,47; Num. 3:20; 33-37; 4:29-33,42-45; 7:8; 10:17-21). They followed after Judah's standard, and before Reuben's in the march, to set up the tabernacle against the Kohathites' arrival.
Their charge was the tabernacle boards, pillars, etc., four wagons and eight oxen being assigned them. Joshua assigned them 12, cities out of Reuben, Gad, and Zebulun (Josh. 21:7,34-40). They shared with the Gershonites and Kohathites the offices of singers, doorkeepers, etc., under David (1 Chr. 15:1-6; 23:5,6,21-23; 26:10,19); in Nehemiah's time also (Neh. 11:15,16).
Lord A. Hervey (Smith's Dictionary) supposes Jeduthun the patronymic title of the house, Ethan the head in David's time, and that Jeduthnn was brother of an ancestor of Ethan before Hashabiah (1 Chr. 6:45; 25:3,19) and son of Hilkiah or Amaziah. Thus, the "sons of Ethan" are distinct from "sons of Jeduthun," and the difficulty is explained how in David's time there could be sons of "sons of Jeduthun" above 30 years of age for they filled offices (1 Chr. 26:10; 16:38), at the same time that Jeduthun is said to be" chief of the singers."
IBSE, "Isaac" (in the public domain) with minor edits.