What prompted Ya'akov to ask who his grandchildren were?
Rashi: When he wanted to bless them, the Shechinah left him, and he wondered why Yosef had children not worthy of being blessed. 1
Rashbam and Seforno: then the Torah states (in Pasuk 10) that Ya'akov 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. Consequently, although he was able to discern Efrayim and Menasheh as two people, he was unable to recognize them.
Rashi: And he saw that Resha'im were destined to descend from them (Yerav'am and Achav from Efrayim and Yeihu and his sons from Menasheh). 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)
רש"י: בקש לברכם: מנין לפירש כך?