Joseph takes his two sons, Ephraim and Manasseh, to his father Jacob for a proper farewell (48:1-22). Jacob proceeds to adopt Joseph's two sons as his own, thereby placing them on a par with his actual twelve sons. To conclude the adoption ceremony, a ritual of blessing follows (48:8-20). Jacob designates Ephraim (the youngest) as the more preeminent--so prominent that in time the entire northern kingdom becomes known as Ephraim.
Jacob's blessing of Joseph (48:15-16) includes the two sons. The language of the blessing gathers themes from the Genesis narrative. Its threefold character reminds one of the Aaronic blessing (Numbers 6:23-26). God is the one before whom Abraham and Isaac walked. God is the one who has been Jacob's shepherd all the days of his life, evoking his own experience of divine guidance, protection, and provision for the journey. God (the angel is God in human form) is the one who has redeemed him from all harm. The story of God's activity on behalf of Jacob's family is now to include the stories of Joseph's sons, who receive the promises given to the chosen family.
15He blessed Joseph, and said,
The God before whom my ancestors Abraham and Isaac walked,
the God who has been my shepherd all my life to this day,
16 the angel who has redeemed me from all harm, bless the boys;
and in them let my name be perpetuated, and the name of my ancestors Abraham and Isaac;
and let them grow into a multitude on the earth.
New Revised Standard Version Bible: Anglicized Edition, copyright © 1989, 1995 National Council of the Churches of Christ in the United States of America. Used by permission. All rights reserved worldwide. http://nrsvbibles.org