Ibzan had many children, which is only possible with a sizable harem. He had thirty sons and thirty daughters. This contrasts sharply with Jephthah and his single daughter, whom he killed. After Jephthah’s desolation comes Ibzan’s fullness. That the judge immediately before Jephthah was Jair, who had thirty sons, only highlights further the fact that Jephthah had only one child.
9 He had thirty sons, and thirty daughters he gave in marriage outside his clan, and thirty daughters he brought in from outside for his sons. And he judged Israel seven years.