Actually Kenaz was Caleb's brother and Othniel was Caleb's nephew.
Joshua 15:16,17 And Caleb said, He that smiteth Kirjathsepher, and taketh it, to him will I give Achsah my daughter to wife. And Othniel the son of Kenaz, the brother of Caleb, took it: and he gave him Achsah his daughter to wife.
Judges 3:9 And when the children of Israel cried unto the LORD, the LORD raised up a deliverer to the children of Israel, who delivered them, even Othniel the son of Kenaz, Caleb's younger brother.
I hope you have found this helpful.