Younger son of the patriarch Joseph (Genesis 41), born in Egypt, during the seven years of plenty.
The first indication of the superiority of Ephraim over his elder brother, Manasses, is seen in the blessing given by their grandfather Jacob (Genesis 48).
Using the power given to him by Divine promises, Jacob adopts as his sons, Manasses and Ephraim, in order that these might form not two branches of the same tribe, but two distinct tribes.
Jacob gives the preference to the younger, by placing his right hand over the head of Ephraim.
New Catholic Dictionary