That Jair had thirty sons was not in and of itself problematic. Psalm 127:1–5 says that many sons are a gift from God. But Jair’s having many sons implies that he had multiple wives. There is a Gideon-like aura about this reference: Gideon had seventy sons…for he had many wives
(Judges 8:30). That did not turn out well for Gideon, or Israel for that matter. One of those sons was Abimelech. And we need to recall that polygamy was forbidden on in the Mosaic law, especially for kings and those in authority (Deuteronomy 17:17). This is a problem for Jair, with his multiple wives, his thirty pampered sons with their donkeys and cities. He obviously had a tendency to accumulate personal wealth, much like Abimelech. We have a man who, in contrast to Tola, acts like an ancient Near Eastern king. He seemingly had his harem. He certainly had his sons riding on donkeys in order to flaunt their wealth and power. There is a real aura of royalty between Jair and his princelike sons. There is a dynastic tendency in this family.1
4 And he had thirty sons who rode on thirty donkeys, and they had thirty cities, called Havvoth-jair to this day, which are in the land of Gilead.