Albert Barnes 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 - This name occurs nowhere else among the families of Benjamin, or in the genealogy of Saul. (See 1 Samuel 9:1 note.)