Shobi’s father may have been the king of the Ammonites, and Shobi appointed by David as tributary king or governor of Ammon after he took Rabbah 2 Samuel 12:29. On the other hand, Nahash may have been a common name among the Ammonites, and the Nahash of 2 Samuel 17:25 may have been of that nation.
On Machir, see the marginal reference.
Barzillai was ancestor, through a daughter, to a family of priests, who were called after him “sons of Barzillai,” and who returned from captivity with Zerubbabel, but were not allowed to officiate as priests, or eat of the holy things, through defect of a proper register Ezra 2:61-63. It is likely that being wealthy they had neglected their priestly privileges, as a means of maintenance, before the captivity.
Rogelim was situated in the highlands of Gilead, but the exact situation is not known. It means “the fullers,” being the plural of the word “Rogel,” in “En-Rogel,” 2 Samuel 17:17.