Malbim: Meforshim ask this. Why did they assume that all of them were born in the 34 years? Perhaps most were born earlier! If Yehoshua ben Yehotzadak returned from Bavel at the age of 105, and each son listed here was born when his father was 15, Shimon ha'Tzadik ¹ was already born when Yehoshua was 90. If so, Shimon was 15 when Bayis Sheni was built, and 45 when he greeted Alexandrus. If Yehoshua was 90 when he returned, Shimon was 30 when he greeted Alexandrus. We find that when the wall was finished, Elyashiv was called Kohen Gadol. After Binyan Beis ha'Mikdash, Yehoshua died and Yoyakim became Kohen Gadol. He died (also he was old), and Elyashiv became Kohen Gadol. Perhaps he and his sons lived many years, and they appointed Shimon ha'Tzadik, for he was worthier than his ancestors. Perhaps one or two of them were appointed Kohen Gadol, or all of them did via an occurrence, e.g. the Kohen Gadol became Tamei ² . We need not say that a later author added matters to Nechemyah - that is very difficult. We can say similarly about the nine generations from Yechanyah mentioned in Divrei ha'Yamim [like I explained in Divrei ha'Yamim I, 3:24].