Why is Saul's family listed twice?

The chapter doesn't say. 9:35-44 gives again, nearly name for name, the family of 8:29-38, from the father of Gibeon to the six sons of Azel. Both have "Ner became the father of Kish. Kish became the father of Saul. Saul became the father of Jonathan, Malchishua, Abinadab, and Eshbaal" (9:39; 8:33). The two lists differ in places: chapter 8 has "The father of Gibeon, whose wife’s name was Maacah" (8:29), and chapter 9 names him, "Jeiel the father of Gibeon, whose wife’s name was Maacah" (9:35); chapter 9 has Ner among his sons (9:36), where 8:30 does not. Chapter 8 goes on past Azel to "The sons of Eshek his brother" (8:39); chapter 9 stops at "These were the sons of Azel" (9:44). What the text does show is what comes next. The very next verse is "Now the Philistines fought against Israel" (10:1), and chapter 10 tells of Saul's death. The book doesn't explain the differences between the two lists, and this study doesn't either.