These verses are the very same with Ch1 8:29-38, giving an account of the ancestors of Saul and the posterity of Jonathan. There it is the conclusion of the genealogy of Benjamin; here it is an introduction to the story of Saul. We take the repetition as we find it; but if we admit that there are in the originals, especially in these books, some errors of the transcribers, I should be tempted to think this repetition arose from a blunder. Some one, in copying out these genealogies, having written those words, Ch1 9:34 (These dwelt in Jerusalem), cast his eye on the same words, Ch1 8:28 (These dwelt in Jerusalem), and so went on with what followed there, instead of going on with what followed here; and, when he perceived his mistake, was loth to make a blot in his book, and so let it stand. We have a rule in our law, Redundans non nocet - Redundancies do no harm.

And Ahaz - This is added by our translators from Ch1 8:35, but such liberties should only be taken in a note; for although the words are now sufficiently distinguished from the text by being printed in Italics, yet it is too much to expect that every editor of a Bible will attend to such distinctions, and in process of time the words will be found incorporated with the text.
Ch1 9:35, and the following verses, are a repetition of what we find in Ch1 8:29-38 (note), where see the notes.

And in Gibeon dwelt the father of Gibeon,.... Whose name is here mentioned, which is not in Ch1 8:29. Jehiel:

whose wife's name was Maachah; as there, but here called his sister, as a wife sometimes is, Gen 20:2. From hence to the end of the chapter is a repetition of the ancestors and posterity of Saul king of Israel; which is made to lead on to and connect the following history of the kings of Judah, begun in this book, and carried on in the next unto the Babylonish captivity, see Ch1 8:29, and the notes there.

Next: 1 Chronicles Chapter 10

the king's gate--The king had a gate from his palace into the temple (Kg2 16:18), which doubtless was kept constantly closed except for the monarch's use; and although there was no king in Israel on the return from the captivity, yet the old ceremonial was kept up, probably in the hope that the scepter would, ere long, be restored to the house of David. It is an honor by which Eastern kings are distinguished, to have a gate exclusively devoted to their own special use, and which is kept constantly closed, except when he goes out or returns (Eze 44:2). There being no king then in Israel, this gate would be always shut.

Next: 1 Chronicles Chapter 10