What prompted Yaakov to ask who his grandchildren were?
Rashi: When he wanted to bless them, the Shechinah left him, and he wondered how Yosef had children not worthy to be blessed. 1
Rashbam, Seforno, Ohr ha'Chayim #1: When the Torah states (48:10) that Yaakov could not see, it does not mean that he was blind (like his father Yitzchak was when he blessed him), but that his eyesight was poor. 2 Consequently, although he was able to discern Efrayim and Menasheh as two people, he was unable to recognize them.
Ohr ha'Chayim #2, Ha'amek Davar: He asked in order to arouse his love before he will bless them, so the Berachah will be with more love. When he hears his son say "they are my sons" (48:9), his innards will warm for them -"mi'Dei Daberi Bo 3 ... Hamu Me'ai Lo" (Yirmeyah 31:19).
Malbim: Yisrael wore different clothing than the Egyptians. Yosef's sons wore like the garments of the Egyptian officers. 4 We find that R. Gamliel's house changed their conduct due to honor of the kingship!
He saw that Resha'im were destined to descend from them (Yarav'am and Ach'av from Efrayim, and Yehu and his sons from Menasheh [Rashi]). This is difficult to understand however, seeing as Resha'im also descended from many of the other tribes - even some of the kings of Yehudah were wicked. (EC)
Ha'amek Davar: The verse did not yet say that his eyes grew weak! Also, he should have recognized from their heights and general form which is Menasheh and which is Efrayim! And if Yosef came to tell him who they are, it would suffice to say "Banai Hemah"!
Harchev Davar: If one discusses a person that he does not love or hate, the first time he says his name, and afterwards, a pronoun (he or him). If he hates him, he does not mention his name at all. Sha'ul called David "Ben Yishai" (Shmuel I 20:27), and Shlomo said to Evyasar "Anasos Lech El Sadecha" (Melachim I 2:26), i.e. he called him Anasos, based on his city. If he loves the person, he constantly mentions him by name. "Hashem Zecharanu Yevarech" (Tehilim 115:12) - when Hashem mentions our name, He blesses us.
Surely Yaakov had seen them often. Efrayim used to learn with him (Rashi to 48:1)! Perhaps they wore like the Egyptian officers only on special occasions. (PF)
Why is he called Yisrael in this Pasuk?
Ha'amek Davar: Now he prepared himself to bless with Ru'ach ha'Kodesh (he was at a higher level).
QUESTIONS ON RASHI
Rashi writes: "Yisrael saw Yosef's sons, [and said, 'Who are these?'] - He had wanted to bless them, and the Shechinah left him...." Why interpret this way?
Gur Aryeh: Had Yaakov never seen Yosef's sons, that he would need to ask who they were? Rashi (to 48:1) wrote above that Efrayim learned with Yaakov regularly! Rashi therefore interprets as, 'why are they unfit for a blessing?' 1
In other words, Gur Aryeh explains that the Pasuk must mean that Yaakov now saw some new dimension of Yosef's sons, that he was unaware of before - that Yarav'am, Ach'av and Yehu would descend from them. (EK)
