The astute reader will notice that “Caleb” in v. 18 doesn’t appear in the list of Hezron’s sons from v. 9. But that’s because “Chelubai” is a variant of “Caleb”, and they are in fact the same person. This Caleb is also not to be confused with “Caleb the son of Jephunneh” from Numbers 13, who was one of the twelve spies sent to spy out the land, who alone with Joshua gave a good report to the people. Even though that Caleb was from the tribe of Judah, I don’t see any mention of Jephunneh in this genealogy.
Hezron’s family, particularly Caleb’s branch, is kind of a mess. Multiple wives, some of them passed from father to son. Hezron himself married again after he was sixty years old, which is fine except that his wife then had children which means she was much younger than him.
Jerahmeel’s branch fares better, though it’s the only one where we are told certain sons died childless. This is also the only place where the names of Jerahmeel’s descendants are recorded. These families lived in the southern part of Judah’s territory. The story of Sheshan’s daughter married to his Egyptian slave is a bit curious, as most Israelites would want their daughters to marry within the same tribe, to keep the inherited land within the tribe. However, David himself had a Moabite for an ancestor in Ruth. This is especially curious considering how much Ezra and Nehemiah were fighting the ungodly cultural influence of foreign husbands and wives among the Jews of their day, returning to the land after the Exile.
All of Your words are given with purpose. Illumine our hearts with Your truth.