‘And he had forty sons, and thirty grandsons, who rode on seventy ass colts.'
He had an abundant family, described in this way to bring to the number seventy, divine perfection intensified. Compare Gideon (Judges 8:30). The fact that they rode on ass colts demonstrates that they exercised authority.
‘And he judged Israel eight years.'
He clearly began to judge while quite old to have so many grandsons. These judges may have been partly contemporary. He too had the privilege of divinely appointed authority over some of God's people.