Zephaniah 1:1 (ESV)

1 The word of the LORD that came to Zephaniah the son of Cushi, son of Gedaliah, son of Amariah, son of Hezekiah, in the days of Josiah the son of Amon, king of Judah.

Josiah’s father was Amon, who reigned from 642 to 640 BC. He, like Manasseh his father in the years before his repentance, was wicked, reverting to the early evil ways of his father. He only ruled two years before being assassinated by his servants (2 Kings 21:19–23; 2 Chronicles 33:20–24).