Radak #1: Giv'on was a city of Binyamin, like it says in Yehoshua. Giv'on's father built it, and it was called on his name.

Radak #2: Really, his name was Ye'i'el, like it says below (9:35). When this lineage is repeated. He is called "Avi Giv'on", for he was the greatest of the city Giv'on. He did not mention [here Ner with ¹ ] Ba'al and Nadav; the second time, he mentioned Ba'al, Ner and Nadav.

'Rashi' citing Yerushalmi, Sof Megilah: Ezra found three Seforim - Sefer Me'onim, Sefer Zatuti, and Sefer ha'Achim. [When there was a difference,] he rejected the one that differs, and sustained the two that agree. They found many Seforim of lineage. When there were three or five, he rejected the minority opinion, and sustained the majority. When he found pairs (some have one version, and an equal number have another version), e.g. "uv'Giv'on Yashvu Avi Giv'on" (9:35), he needed to write it twice - here, and in his Sefer. Why did he not write both here, i.e. also "v'Eleh Roshei ha'Medinah"? Since there he traced the lineage until "v'Eleh ha'Kohanim ha'Leviyim", until Yedayah, who was after Ezra, why should he teach here in Divrei ha'Yamim [also] what was after Ezra ¹ ? Rather, here teaches only those in Bayis Rishon, and the other Parshah of uv'Giv'on Yashvu. Chachamim also said in Pesachim (62b) there are 13,000 ² camels laden with Drashos about "ul'Atzal Shishah Banim."

Malbim: He also had a sister Ma'achah.

Minchas Shai (9:35): In all early texts, also below it says Ishto. 'Achoso' is a mistake.