No, its not a Bible contradiction.  There are two kings by the same name ruling at the same time.

Introduction

Here you will see a solution to the problem of Ahaziah’s age found in 2 Chronicles 22:2 and 2 Kings 8:26.  In the former verse, he is said to be 42 years old and in the latter verse he is said to be 22 years old. The solution is that he is not the same man.  There are two Ahaziah’s. The first Ahaziah is the son of Athaliah, the daughter of Omri.  This child was born to her before she married Jehoshaphat.  So, he was also Jehoshaphat’s stepson. This boy was 42 years old when he took the throne from Jehoram, king of Judah.

The second Ahaziah is the son of Athaliah, who was the daughter of Ahab.  The confusing thing is that she is also called “the daughter of Omri.”  In fact, she was his granddaughter.  This child was the youngest son of Jehoram and Athaliah.  He was 22 years old when he took the throne of Jehoram, king of Judah.

Both of these Ahaziah’s were killed by Jehu and they were succeeded in their reign by Athaliah, the widow of Jehoshaphat.  She reigned seven years, coincident with the first seven years of the reign of Jehu in Israel.

Here are the verses that show that the above facts are true.  According to 1 Kings 22:41-42, Jehoshaphat begins to reign in Judah during the fourth year of Ahab’s reign in Israel. Jehoshaphat reigns for 25 years.  According to 2 Chronicles 17: 1, Jehoshaphat’s reign began while Judah and Israel were still enemies.

The Older Ahaziah – Jehoshaphat’s Stepson

However, after Jehoshaphat got rich he “joined affinity with Ahab” (2 Chronicles 18: 1).  “Affinity” means to establish a relationship by marriage.  Here, he marries Athaliah, the daughter of Omri (2 Chronicles 22:2) who happens to be Ahab’s sister (1 Kings 16:29).  It is important to note that since Jehoshaphat only reigns 25 years, and he is succeeded by Jehoram who reigns 8 years, any child that Jehoshaphat has by Athaliah could not possibly be more than 33 years old (25 years for Jehoshaphat’s reign plus 8 years for Jehoram’s reign equal 33 years) by the time Jehu begins to reign in Israel.  Since Athaliah has a son who is 42 years old at the end of Jehoram’s reign, her son cannot be the literal seed of Jehoshaphat.  He is a stepson.  Understanding this helps to reconcile three difficulties with the older Ahaziah.

• First, Jehoram is the “firstborn” son of Jehoshaphat (2 Chronicles 21: 3).  When he dies at 40 (2 Chronicles 21: 20), Ahaziah is two years older than he is.  Therefore, if Ahaziah were the literal offspring of Jehoshaphat, Jehoram would not have been the firstborn.
• Second, Jehoram is said to have killed all of his brethren with his sword (2 Chronicles 21: 4), who were of his father’s house (2 Chronicles 21: 13).  There is no problem to reconcile here because Ahaziah is adopted.
• Third, Ahaziah is said to be the son of Jehoshaphat in 2 Chronicles 22:9.  As a stepson, this would be true.  So, three problems are immediately solved.

Jehoshaphat’s Co-reign with the King of Judah and His Reign over Israel

Jehoshaphat actually reigns, for a period of time, over both Judah and Israel.  To see this, we have to untangle some of the dates and names of kings in both Judah and Israel.

• Ahab dies and is succeeded by Ahaziah in Israel during the 17th year of Jehoshaphat (1 Kings 22:40, 51).
• Ahaziah’s reign in Israel only lasts two years and he dies in 2 Kings 1: 7 & 17.
  In the 18th year of Jehoshaphat, Jehoram begins to reign in Israel, = and his reign lasts for 12 years (2 Kings 3: 1).
• When Jehoram begins to reign in Israel, Jehoshaphat has 7 to 8 years left on his reign in Judah.

Now notice something very interesting.  There is a king Jehoram reigning in Israel, and there is a king Jehoram reigning in Judah. Jehoram, in Judah, begins to reign during the fifth year of Jehoram’s reign in Israel (2 Kings 8:16). Therefore, Jehoshaphat still has two to three years left on his reign.  That’s why 2 Kings 8: 16 says” Jehoshaphat being then king of Judah.”  He isn’t dead yet. Jehoshaphat co-reigns with Jehoram in Judah.  It is at this time that he assumes control over both Israel and Judah and is therefore called the “king of Israel” (2 Chronicles 21: 2).

How the 42 Year-old Ahaziah gets to the Throne

Jehoshaphat dies while both Jehoram’s are still reigning. Jehoram, in Judah, gets sick with an incurable disease during the last two years of his reign in Judah. Before Jehoram in Judah dies, Athaliah (Jehoshaphat’s widow) puts her 42 year old son, Ahaziah, on the throne.  This is done during the 11th year of Jehoram’s reign in Israel, just 6 to 7 years after Jehoram was put on the throne in Judah (but obviously before his death, since he reigned 8 years).

How the 22 Year-old Ahaziah gets to the Throne

Shortly after the older Ahaziah takes the throne in Judah, Jehoram’s 22 year old son also takes the throne in Judah, since he is the heir by birth to the reigning king in Judah (evidently planning to have the older Ahaziah assume control of both Judah and Israel, like Jehoshaphat did).  This is Jehoram’s youngest son (also called” Jehoahaz”), who reigns because his older brothers were killed by the Arabs (2 Chronicles 21: 17; 22: 1).  The younger Ahaziah ascends to the throne during the 12th year of Jehoram in Israel.

The Two Athaliah’s – Mothers of the Two Kings

• Athaliah the daughter of Ahab. The 22 year old Ahaziah is the son of Jehoram, king of Judah, and Athaliah the daughter of Ahab (2 Kings 8:25, 18).  She’s also called “Athaliah, the daughter of Omri, king of Israel,” in 2 Kings 8:26.  However, she is his granddaughter.  Consequently, the 22 year old Ahaziah is the “son-in-law of the house of Ahab” (2 Kings 8:27).
• * Athaliah the daughter of Omri.  Since there are two Athaliah’s, it is said of the mother of the 42 year old Ahaziah, “His mother’s name ALSO was Athaliah the daughter of Omri” (2 Chronicles 22:2).  That “ALSO” is very important when you consider that Jehoram’s wife and Jehoshaphat’s wife both go by the same name.

The Length of the Ahaziahs’ Reigns

Both of the Ahaziah’s are said to have reigned for one year.  Evidently, the older Ahaziah reigns just a little bit longer than the younger one, since he starts a little earlier. Both of these men were killed by Jehu.  It is in the analysis of their deaths that you can see that there really are two Ahaziah’s reigning jointly in Judah.

How They Died – The Key

• 2 Kings 9:27-28 records the death of the younger Ahaziah.  Right after Jehu shot Jehoram, king of Israel, Ahaziah fled by the way of the garden house.  Jehu himself followed after him and instructed his men to smite him while he was in his chariot. They did this in a place called Gur, just outside of Ibleam, which is north of Samaria. Ahaziah was able to flee in his chariot all the way to Megiddo, where he finally died. Following his death, his servants carried him in a chariot to Jerusalem and buried him there in the sepulcher of his fathers.
• 2 Chronicles 22:7-9 records the death of the older Ahaziah.  Like the younger Ahaziah, he had gone to see Jehoram, king of Israel. Jehu’s men found Ahaziah when they were looking for him, while he was hidden in Samaria.  They caught him and brought him to Jehu. When they killed him, THEY buried him.  The reason that they said that they buried him was that “he is the son of Jehoshaphat.”

Notice the differences in the deaths of the two Ahaziah’s. One was shot in his chariot and fled to Megiddo.  He was then taken by his servants back to Jerusalem to be buried.  The other was caught and brought to Jehu, where he was slain before him and buried.  These are obviously not the same man.

Conclusion

So, the Ahaziah of 2 Chronicles 22:1 is the 22 year old Ahaziah, who is the youngest son of Jehoram, king of Judah.  The Ahaziah of 2 Chronicles 22:2 is the 42 year old son of Athaliah, who was also the stepson of Jehoshaphat.  It should be no surprise that Athaliah would promote her own son to the throne of Judah.   After all, she was a direct descendant of Omri and a sister to Ahab, the wickedest king that Israel ever had.  Furthermore, it is obvious that she intended to have influence over the throne, since she took the throne herself after the death of her son (2 Chronicles 22:10-12).  The successor to the throne after Athaliah’s seven year reign, which coincides with Jehu’s first seven years as king over Israel, was Joash, who is the son of the 22 year old Ahaziah.