2 Kings 21:1

Manasseh was twelve years old - Manasseh, therefore, was not born at the time of Hezekiah’s dangerous illness; and it is probable that Hezekiah had at that time no son to succeed him. According to Josephus, this was the principal cause of his grief.

Hephzibah - Jewish tradition makes Hephzibah, Hezekiah’s wife, the daughter of Isaiah; but this is scarcely probable. She was, however, no doubt, known to the prophet, and it may well have been in special compliment to her that Isaiah introduced her name Isaiah 62:4 as one that Jerusalem would bear after her restoration to God’s favor. The name means, “My delight (is) in her.”