There are some New Testament allusions or quotations in the King James Version (KJV) that don't precisely match the Old Testament (KJV) source that they point to; however, such allusions or quotations may match the Brenton LXX sources better. Therefore, did Lancelot Charles Lee Brenton borrow from the KJV when translating or editing his English Septuagint?
One example is 1 Peter 4:18, which alludes to Prov. 11:31:
1 Pe 4:18 KJV
And if the righteous scarcely be saved, where shall the ungodly and the sinner appear?
Pro 11:31 KJV
Behold, the righteous shall be recompensed in the earth: much more the wicked and the sinner.
Pro 11:31 LXXE
If the righteous scarcely be saved, where shall the ungodly and the sinner appear?
Another example is Hebrews 1:6, which alludes to Deuteronomy 32:43:
Heb 1:6 KJV
And again, when he bringeth in the firstbegotten into the world, he saith, And let all the angels of God worship him.
Deu 32:43 KJV
Rejoice, O ye nations, with his people: for he will avenge the blood of his servants, and will render vengeance to his adversaries, and will be merciful unto his land, and to his people.
Deu 32:43 LXXE
Rejoice, ye heavens, with him, and let all the angels of God worship him; rejoice ye Gentiles, with his people, and let all the sons of God strengthen themselves in him; for he will avenge the blood of his sons, and he will render vengeance, and recompense justice to his enemies, and will reward them that hate him; and the Lord shall purge the land of his people.