The king’s bodyguard included the Cherethites and Pelethites, who were likely foreigners. The Cherethites might have come from Crete (see also 1 Samuel 30:14; Ezekiel 25:16). These groups could have been Philistine mercenaries.
David’s sons were priestly leaders: David was from Judah and not a Levite (only people from the tribe of Levi could usually serve as priests). David may have created a new group of religious servants connected to his family line of kings to serve the king's court. This was different from the normal priests who served at the temple (see also study note on 2 Samuel 20:26).