Commentary for Numbers 32:12

הקנזי [CALEB THE SON OF JEPHUNNEH] THE KENEZITE — He (Caleb) was the stepson of Kenaz (and therefore he is termed here the Kenezite), and Caleb's mother bore Othniel to him (to Kenaz) (and for this reason Othniel, the son of Kenaz is described in Joshua 15:17 as Caleb’s brother) (Sotah 11b).

בלתי כלב בן יפונה הקנזי, “except for Calev, son of Yephuneh the Kenizite.” Our sages (Sotah 11) derive from here that Calev was a stepson of Kenaz for whom the mother of Calev had born Othniel.

To whom Kaleiv’s mother bore Osniel. Rashi wishes to answer the question: Here it is written “Kaleiv son of Yefuneh, the Kenizite.” But if he was the son of Yefuneh then he was not the son of Kenaz, and if he was the son of Kenaz then he was not the son of Yefuneh. Furthermore, elsewhere it only writes Kaleiv son of Yefuneh. He answers that here when it is written, “Son of Yefuneh, the Kenizite” the meaning is as follows: After Yefuneh, Kaleiv’s father, died his mother married Kenaz and bore him Osniel. Thus, Kaleiv was called “son of Yefuneh” [who was his biological father] his father, and [he was also called] “the Kenizite” the name of his mother’s husband.