1)
Do we know anything about Kenaz?
1.
Radak: No. Even though he was not mentioned, his descendants are taught.
2.
Malbim: The first Kenaz was from Ashchor, and he gave birth to Yefuneh. Therefore, it says Kalev ben Yefuneh ha'Kenazi. Yefuneh had two sons - Kalev and Kenaz. Therefore, it says "Osni'el ben Kenaz Achi Kalev" - Kenaz, Osni'el's father, was Kalev's brother. We already knew this from the Torah and Sefer Yehoshua! Here it teaches about the sons of Kenaz ben Yefuneh.
2)
It says "u'Vnei Osni'el", but only one is listed!
1.
Malbim: "U'Me'onasi" at the start of the coming verse applies also to u'Vnei Osni'el.
