Charles Ellicott Commentary 2 Chronicles 27:8

"He was five and twenty years old when he began to reign, and reigned sixteen years in Jerusalem." — 2 Chronicles 27:8 (ASV)

He was five and twenty years old.—A word-for-word repetition of 2 Kings 15:33, omitting the last clause about the queen-mother. Perhaps in one of the chronicler’s sources this notice occurred at the beginning, and in another at the end of the reign. This would account for its repetition here, after having been already stated in 2 Chronicles 27:1.