Charles Ellicott Commentary 1 Samuel 10:21

"And he brought the tribe of Benjamin near by their families; and the family of the Matrites was taken; and Saul the son of Kish was taken: but when they sought him, he could not be found." — 1 Samuel 10:21 (ASV)

The family of Matri was taken. —In none of the Benjamite genealogies connected with the royal house of Saul does this name occur. We cannot account for the omission. Ewald conjectures that the name Matri is a corruption from “Bikri” (see 1 Chronicles 7:8).