Genesis 48:15

And he blessed Joseph, and said: The Lord, before whom my fathers Abraham and Izhak, did serve; the Lord who hath fed me since I have been unto this day,

AND HE BLESSED JOSEPH, AND SAID. The meaning of this verse 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 future 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’) 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. 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, (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, 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.

ויברך את יוסף, there was no need for him to see Joseph then in order for this blessing to be effective, neither was there any need for kissing or embracing. The precise nature of Yaakov’s blessing for Joseph at this point has not been spelled out.

האלוקים אשר התהלכו אבותי לפניו, as if he had addressed G’d in a preamble to the blessing, saying: “You are the G’d before Whom my fathers walked steadfastly, etc.; please do what I ask for the sake of their merit.”

האלוקים הרועה אותי, the same G’d Who has acted as my own shepherd, i.e. “You Who have shown me so much love.”

ויברך את יוסף, anyone blessing his sons, automatically was conferring a blessing on him also.

אשר התהלכו אבותי לפניו, I have already explained on Genesis 17,1 that this wording includes serving G’d in one’s heart as well as with deeds. The root of all religious service is in the heart. [when it is only the from the lips outward it is a sham. Ed.] We must not understand Yaakov as claiming credit for himself or boasting, that he himself had served G’d, although it is a fact that he had served the Lord; he meant to give credit to his fathers, suggesting that if G’d had been at his side this had been largely due to the merits of both his father and grandfather. המלאך, having first spoken about G’d having assisted him, and creating the impression that G’d, personally, had done so, he now mentions the intermediary always used by G’d to do His work. We know from Psalms 34,8 חונה מלאך ה' סביב ליראיו ויחלצם, “G’d’s angel camps around those who fear Him and He rescues them,” that His agents called מלאכים are close at hand whenever the righteous are in danger. This is why Yaakov at this time referred to המלאך הגואל אותי מכל רע, the one sent by G’d to rescue him, protect him, and bless him, יברך את הנערים will function similarly and protect Joseph’s sons. We know that such angels had been in evidence protecting Yaakov first from Lavan, then from Esau, and again when the Emorites launched an attack after Yaakov’s sons had killed the males of Shechem and looted the town.