An extract from BHFA Volume 5
2 Chronicles 36:9a
בֶּן־ שְׁמוֹנֶה שָׁנִים יְהוֹיָכִין בְּמָלְכוֹ
when his reign (began) Jehoiachin years eight son (old)
In BHS, a footnote at the second word of this verse suggests that we insert עֶשְׂרֵת which means, "ten." This would then agree with some versions of the LXX, and also with 2 Kgs 24:8 which has בֶּן־שְׁמֹנֶה עֶשְׂרֵה שָׁנָה meaning, "son (old) eight."
Except for KJV, all other major English translations follow the footnote's suggestion.
To motivate this they refer to 2 Kgs 24:15 which states that he had "wives," and to Jer 22:38 which states that he had "seed."