Commentary for Genesis 48:15

AND HE BLESSED JOSEPH, AND SAID. The meaning of this verse⁴⁸The verse begins by stating that Jacob blessed Joseph, and the blessing that follows refers only to his sons. Ramban is attempting to resolve this difficulty. is that in order to bless Joseph, out of his love for him, he blessed his sons. Scripture is relating that Joseph had no other children and his entire blessing was inherent in the blessing of these boys. It may be that [the blessing here was directed at Joseph himself, stating that] the other children who will be born to him in the future⁴⁹Verse 6 here. shall be called by the name of their brothers and be blessed with their blessing.
In my opinion this latter interpretation is correct since the prophet Jacob said, And the children that were born (‘holad’to’)⁵⁰Holad’to is in the past tense and means “were born to you.” Ramban will explain that Jacob’s words are to be understood as if they were in the future tense: “And the children that will be born to you after them shall be thine.” Joseph thus had other children besides Ephraim and Menasheh, whom Scripture does not record, as they were counted among the tribes of his first sons. after them, shall be thine, and his word would not be in vain.⁵¹As it would be if we interpret the verse literally as referring to the past for Joseph did not as yet have any children other than Ephraim and Menasheh. However, Joseph did beget children after that, just as is the opinion of Onkelos, who translated: “And the children that you will beget after them.” And thus, asher holad’to is a past tense replacing a future, just as in the verse, Which I took out of the hand of the Amorite,⁵²Verse 22 here. Here again, lakachti (I took) is to be understood as if it were in the future tense. and many additional verses besides. Even in line with the literal interpretation of Scripture it would appear that Joseph had children that he had begotten after his father came to him in Egypt. This is obvious from the fact that Jacob found it necessary to elaborate rather than say, “And now thy sons, Ephraim and Menasheh, who were born to thee, shall be mine as Reuben and Simeon, and the children that will be born shall be thine.” This is the reason why Scripture states, And unto Joseph were born two sons before the year of famine came,⁵³Above, 41:50. since after the famine additional children were born to him, but Scripture does not mention them as there is no need for us to know of them [since they were absorbed into the tribes of Ephraim and Menasheh].

ויברך את יוסף, blessings bestowed on one’s children are a blessing bestowed on the father.

He blessed Yoseif. Scripture does not relate the contents of this blessing.