Ahaziah of Judah or Jehoahaz I, was the sixth king of Judah, and the son of Jehoram and Athaliah, the daughter (or possibly sister) of king Ahab of Israel. He was also the first Judahite king to be descended from both the House of David and the House of Omri, through his mother and successor, Athaliah.

According to 2 Kings 8:26, Ahaziah was 22 years old when he began to reign, and reigned for one year in Jerusalem. 2 Chronicles 22:2 gives his age as 42 years when his reign began in Jerusalem. Most scholars regard the 42 years in [2 Chronicles 22:2] as a copyist’s error for an original 22 years. The age of 22 is also found in some Greek and Syrian versions of [2 Chronicles 22:2].

Second Question: King Jehoiachin is mentioned in [2 Chronicles 36:9] as being 8 years old when he began to reign, but in [2 kings 24:8] he is mentioned as being 18 years.