John Gill Commentary Genesis 46:20

"And unto Joseph in the land of Egypt were born Manasseh and Ephraim, whom Asenath, the daughter of Poti-phera priest of On, bare unto him." — Genesis 46:20 (ASV)

And unto Joseph in the land of Egypt were born Manasseh and Ephraim

And therefore not to be reckoned with those that went down with Jacob thither; for which reason the clause, "in the land of Egypt", is inserted, see (Genesis 41:50) ;

which Asenath the daughter of Potipherah, priest of On, bore unto him ;

Here again the Targum of Jonathan makes Asenath to be the daughter of Dinah, who it says was educated in the house of Potipherah prince of Tanis; (See Gill on Genesis 41:50).