'Rashi': Above it gave the lineage of part of Kalev's family, and interrupted with Yerachmi'el's lineage. It needed to write Kalev Achi Yerachmi'el, lest one say that Kalev's lineage was already given, so this is a different Kalev. This Sefer often gives part of the lineage of a family, skips to another family, and returns to the first. Malbim - this is like the Pshat. Also refer to 2:42:1:2.

Malbim based on Sotah 11b: Kalev above is Kalev ben Yefuneh. Surely he is not Ben Chetzron - he was Ben Yefuneh ¹ ! Rather, he descended from Chetzron. This Sefer often calls descendants 'sons'. We cannot say that Kalev was Chetzron's son, for the Sefer implies that the three sons were born before he married Bas Machir at the age of 60. Chetzron descended to Egypt, and [211 years later] Kalev was 40 when the Meraglim were sent! (Likewise, Achan is called Ben Zerach (Yehoshua 7), for he descended from him! According to this, until now the Sefer discussed Kalev ben Yefuneh's family. Now it teaches the family of Kalev ben Chetzron, Yerachmi'el's brother.

Radak: Perhaps those mentioned above were more esteemed. His sons from Efras were mentioned for the honor of Betzalel.

Malbim: Before discusses Kalev ben Yefuneh. Here discusses Kalev ben Chetzron, like I explained (refer to 2:42:1:3).

'Rashi': Meisha was the Sar of Zif, all Bnei Mareshah, and of Chevron. These cities are written in Yehoshua 15:24, 44.

Radak #1: Zif was known ¹ [when the Sefer was written]. This is like "Machir Avi Gil'ad" and many verses. It should say u'Vnei Zif Mareshah Avi Chevron; Zif is omitted, for he was already mentioned. The Sefer relies on the reader to understand this.

Malbim: Zif and Bnei Mareshah descended from him. Below (4:21) we find "Ladah Avi Mareshah"; that was a different Mareshah (from Shelah ² ). Mareshah had a son Chevron from whom came great families (the coming verses discuss them).