‘And his father refused and said, “I know, my son, I know. He also shall become a people, and he also will be great, however his younger brother will be greater than he and his seed will become a multitude of nations.” And he blessed them that day, saying, “In you shall Israel bless, saying, ‘God make you as Ephraim and as Manasseh.' And he set Ephraim before Manasseh.'
Jacob is understanding and does not rebuke him. Then he confirms why he has acted as he has. He continues his blessing. Manasseh will become a great people, but Ephraim will be even greater and become a multitude of nations. So much so that when men speak of them in proverb they will always put Ephraim first. But both will be mentioned in the proverb, and there is no greater statement of success than to become a proverb.
That Jacob would become a company of peoples he knew from the covenant promises. That this would be through his sons he must have been aware. Thus this blessing is the natural sequel to that with the additional awareness of the extra success of Ephraim.
And both did become great peoples, but Ephraim became so great a people that all Israel was later named after them because of their superior numbers. Indeed ‘Ephraim' could be called God's firstborn (Jeremiah 31:9). Judges 8:2 already hints at their greatness.
“In you shall Israel bless.” We had the hint in Genesis 47:27 that the name of Israel was beginning to be applied to the tribe. This is confirmed here. The family tribe is now seen as a people.