'Generation' in the Bible

Yahweh said to Jehu, "Because you have done well by doing right in my eyes and you have done to the house of Ahab according to all that [was] in my heart; [therefore,] sons of the fourth generation will sit for you on the throne of Israel."

This is the word of Yahweh which he spoke to Jehu, saying, "Sons of a fourth [generation] shall sit for you on the throne of Israel," and it was so.