Twenty and five years old was he when he began to reign; and he reigned twenty and nine years in Jerusalem. His mother's name also was Abi, the daughter of Zachariah.

He was five and twenty years old when he began to reign: and he reigned nine and twenty years in Jerusalem: the name of his mother was Abi the daughter of Zacharias.

a son of twenty and five years was he in his reigning, and twenty and nine years he hath reigned in Jerusalem, and the name of his mother is Abi daughter of Zechariah.

He was twenty-five years old when he became king, ruling in Jerusalem for twenty-nine years; his mother's name was Abi, the daughter of Zechariah.

He was twenty-five years old when he had begun to reign, and he reigned for twenty-nine years in Jerusalem. The name of his mother was Abi, the daughter of Zechariah.

Twenty and five years old was he - This statement, combined with that of 2-Kings 16:2, would make it necessary that his father Ahaz should have married at the age of 10, and have had a child born to him when he was 11 years of age. This is not impossible; but its improbability is so great, that most commentators suggest a corruption in some of the numbers.
The Zachariah here mentioned was perhaps one of the "faithful witnesses" of Isaiah Isaiah 8:2.

Twenty and five years old was he when he began to reign,.... Now as Ahaz his father began to reign at twenty, and reigned sixteen, he must die at thirty six; so that this son of his must be born to him when at eleven years of age, for only so many years there be between twenty five and thirty six, which may seem wonderful; but, as Grotius observes, Hezekiah had now entered into the twenty fifth year, and he might be just turned of twenty four, and so his father might be twelve years of age at his birth: besides, as it is usual for the divine historian to take away or add the incomplete years of kings, Ahaz might be near twenty one when he began to reign, and might reign almost seventeen, which makes the age of Ahaz to be about thirty eight; and Hezekiah being but little more than twenty four, at his death there were thirteen or near fourteen years difference in their age, and which was an age that need not be thought incredible for begetting of children. Bochart (f) and others (g) have given many instances of children begotten by persons under that age, even at ten years of age (h): four years after his birth, the famous city of Rome began to be founded (i), A. M. 3256, and before Christ 748, as commonly received, though it is highly probable it was of a more early date; according to Dionysius Halicarnassensis, it was founded in the first year of the seventh Olympaid, in the times of Ahaz, A. M. 3118 (k):
and he reigned twenty and nine years in Jerusalem; so that he reigned twenty three years or more after the captivity of the ten tribes:
his mother's name also was Abi the daughter of Zachariah; perhaps the daughter of the same that was taken by Isaiah for a witness, Isaiah 8:3 who very probably was a very good woman, and took care to give her son a religious education, though he had so wicked a father.
(f) Ep. Carbonell. tom. 1. oper. p. 920. (g) Vid. Hieronymi Opera, tam. 3. Ep. Vital. fol. 25. C. (h) T. Bab. Avodah Zarah, fol. 44. 1. (i) Usser. Annal. p. 86, 87. (k) Vid. Breithaupt. Not. in Hist. Gorion. Hebrews. l. 5. c. 1.

To reign - It is not certain that Ahaz lived only thirty six years, for those sixteen years which he reigned, may be computed, not from the first beginning of his reign, when he reigned with his father; which was at the twentieth year of his age, but from the beginning of his reigning alone.