Jamieson, Fausset and Brown on 1 Chronicles 15:4

4. David assembled the children of Aaron, and the Levites--The children of Aaron were the two priests (1Ch 15:11), Zadok and Abiathar, heads of the two priestly houses of Eleazar and Ithamar, and colleagues in the high priesthood (2Sa 20:25). The Levites were the chiefs of their father's house (1Ch 15:12); four belonging to the Kohathite branch, on whose shoulders the ark was to be borne; namely, Uriel, Shemaiah--descended from Elizaphan or Elzaphan--(Ex 6:22), Hebron (Ex 6:18; 1Ch 6:2), and Amminadab from Uzziel (Ex 6:22).