To Be Like Efraim and Menashe
We are told in the Parsha that parents will bless their children with the words, ישימך אלוקים כאפרים וכמנשה, that Hashem should make you like Efraim and Menashe.
One of the reasons for this blessing is that parents are praying that their own children will succeed and maintain their commitment to Judaism, regardless of the challenge. Efraim and Menashe never lived in Israel and lived their entire lives in decadent Egypt. Despite this, they were considered on par with the other tribes of Israel, and they met the challenge.
A second interpretation is that there was great love between the two brothers, and there was no sibling rivalry between them. Some say that Yakov switched his hands to put his right hand over the younger, Efraim, because of his great humility and admiration for his brother.
It is clear why parents would wish that their own children would have the same attributes as Efraim and Menashe.p