Yaacov’s blessing for these two grandsons was “By you shall Israel bless saying “May G-d make you like Ephraim and Menashe” and he put Ephraim before Menashe.
It remains customary for fathers to bless their sons in this way every Shabbat before Kiddush. R’ Eli Munch wrote that Yaacov saw that Yoseph’s two sons were brought up in a foreign land in an environment diametrically opposed to ancestral principles. Despite the attractions of the society around them, they did not exchange their Judaism for high social standing or the brilliant political careers which the Egyptian state offered them.They abandoned their positions in the Egyptian society and joined their relatives, lowly immigrant shepherds, in Goshen. Yaacov expressed the hope that every Jewish father would be able to ensure that his sons understood their heritage and could live by it’s principles and beliefs.
Yaacov placed merit before the privilege of birth in mentioning Ephraim before Menashe, the younger before the elder. This had been a feature in the Torah of the transmission of the heritage on numerous occasions. This time, Yaacov was predicting that Ephraim ‘s descendants would be greater than those of Menashe. Torah study was greater by Ephraim, and Joshua was his descendant. Surely then the blessing implies that present day sons should be meritorious in the conduct of their lives.
R’ Jonathan Sacks quoted his predecessor R’ Jakobovits who noted that this event is a rare example of a grandparent blessing his grandchildren. R’ Sacks showed that the Talmud Bavli argued that the greatest privilege is to teach your grandchildren Torah, while the Talmud Yerushalmi argued that the greatest privilege is for your grandchildren to teach you. R’ Sacks concluded that both these arguments are valid. He showed that those who think about their grandchildren are future oriented, and would care that there was peace for their grandchildren and would work towards it.