'B'cho yevoraich yisroel - yesimcho Elokim k'ephraim v'chimenashe"
We bless our sons that should grow up to be like Ephraim and Menashe. Why not the other shevatim, why dafka these two?
I heard that these two are the ones who grew up in lowly, depraved mitzrayim and still became shevatim! In the long golus, where we are surrounded by tempting, depraved cultures, we bless our sons that they should thrive spiritually, just like Ephraim and Menashe, in spite of the difficult surroundings.
That is our prayer for our children - and so too for ourselves. Let's take chizuk from Ephraim and Menashe and realise that they were chosen because this is the nisayon we are supposed to live through - and yet, we can still raise ourselves to the greatest heights we can possibly reach!