Please see 24:14.
Rashi based on Gemoro Sanhedrin 69b says that Chur was the son of Miriam and Kaleiv ben Yefunneh. The Gemoro is based on Divrei Hayamim 1 2:18 which says Miriam married Kaleiv ben Chetzron. How can this be the same person as Kaleiv ben Yefunneh? If Chetzron was Kaleiv’s father and Kaleiv was 40 when he left Egypt (Yehoshua 14:7) then Chetzron would have been 170 when he had Kaleiv. Chizkuni on Bemidbar 13:6 echoes, but does not defend the Gemoro.
This (according to Ibn Ezra short) show that Yefunneh and Chetzron were different people.
Does anyone defend the Gemoro?
The gemorah in sotah 11b says that Kalev was the son of Chetzron, and Yifuneh was a nickname given to him because he turned away “pina” from the meraglim. See Rashi there. The Talmud Yerushalmi Yevamos 10-1 also says that Calev ben yifuneh was ben Chetzron.
Regarding your second question, this is a known disagreement between rashi and the Ibn Ezra. The Malbim is quoted saying, that Yifuneh was a grandchild to Chetzron. However this will not fit with the Rashi Bereshis 15-16 that there were only four generations, ans Chetzron was the father of Calev. On the other hand we do find other such instances, such as Yocheved having Moshe at age 130.