John Gill Commentary Genesis 45:12

"And, behold, your eyes see, and the eyes of my brother Benjamin, that it is my mouth that speaketh unto you." — Genesis 45:12 (ASV)

And, behold, your eyes see, and the eyes of my brother
Benjamin
They were eyewitnesses of his being alive, having themselves seen him, and even Benjamin, who could not be suspected by his father of a fraud in imposing on him; and some of them could doubtless remember his features, and had an ocular proof of his being the very person, which they could with great evidence relate to Jacob; as also his voice in speaking:

that [it is] my mouth that speaks to you ;
without an interpreter, as Aben Ezra, and in the Hebrew language, as the Targum and Jarchi; which might confirm them, and likewise their father upon their report, that the governor was not an Egyptian, but an Hebrew; and by that and other concurrent testimonies that he must be Joseph.