In this chapter, the genealogy of Judah is concluded and we also read the genealogy of Simeon.
My commentary for this chapter is mostly minor notes, I don't see any big or important structural issues here.
After the previous chapter went deep into the family of David, listing descendants all the way down to the return from the Babylonian exile, this chapter jumps all the way back up to the sons of Judah. Even though all of these people fall under the general category of "sons of Judah", there is a sudden and sharp temporal transition between the "sons of Elioenai" who would have lived c. 500 BCE and Perez son of Judah who would have lived c. 1500 BCE. This is because the genealogy is shifting back from a "vertical" genealogy to a "horizontal" genealogy; since the author is done exploring the family tree of David, we now go back to the broad clans and families of Israel.
Verse 4 concludes the genealogy of Hur, which was interrupted by the family tree of David.
Verses 9-10 contain the prayer of Jabez, which is a very obscure passage but somehow became the title of a famous devotional book. Since this is a moderately famous passage (at least, famous to some people) I feel like I should have something to say about it, but there isn't much that comes to mind. Jabez as a biblical figure is only ever mentioned here and he does nothing. The only thing I can think to say about Jabez is that he overcomes his name, where he was called pain and was born in pain, but God freed him from it.
It's hard to date some of the people in this genealogy. Othniel is one of the first judges, but Caleb son of Jephunneh is a contemporary of Moses who would have died long before Othniel was born. Even though this part of the genealogy is mostly horizontal, not all of these people lived together.
Mered is an obscure figure who is not mentioned anywhere else in the bible, but he marries one of the daughters of Pharaoh. It's possible that Mered was in Egypt before the exodus when Israel dwelt there. I also think it's possible that Mered was a leader in Israel during the later period (e.g. the reign of Solomon) when Israel had a political alliance with Egypt, and the marriage between Mered and Pharaoh's daughter may have been part of that alliance.
Mered must have been a powerful figure to have married a daughter of Pharaoh, but he is comparatively anonymous in the bible. Because the bible is not a story about the rich and powerful, people like Mered are largely ignored. He must have been important in his time, but the bible is a religious history and it does not respect wealth or power when choosing its subjects.
The genealogy of Judah concludes with the sons of Shelah, ending the chiasm that encompasses all the sons of Judah. I talked about this chiasm in the previous two chapters.
I am amused by the phrase in v. 22 where it says "these records are from ancient times". It amuses me that even in the time when Chronicles was written (~400 BCE) the author was quoting from records that are "ancient" to him. It also proves what I had previously asserted, that Chronicles is principally quoting from earlier sources.
For the genealogy of Simeon, v. 33 likely indicates a break between two distinct genealogical records with the phrase "and they kept a genealogical record".
I'm not sure why Simeon is listed second. Generally, the tribes mentioned most prominently in the genealogy and the ones that are most important in the time that Chronicles was written. From their history we knew that Simeon's tribal inheritance was in the midst of Judah, and Simeon as a tribe was gradually absorbed into Judah over the centuries.
Verses 41-43 however shows that Simeon as a tribe was still active, expanding and militarily engaged with their enemies during the time of Hezekiah. It's possible this is why they were included in the genealogy in such a prominent location. It's particularly noteworthy that the people of Judah were still fighting the Amalekites hundreds of years after the Exodus when their first recorded battle occurred.