Genesis 48:1-22

Jacob Blesses Manasseh and Ephraim, the Sons of Joseph

He adopts them as his own sons with privileges equal to the others, thus making them heads of distinct tribes. By so doing he gives to Joseph, the eldest son of Rachel, whom he probably regarded as his true wife, the position of firstborn with a double portion of his inheritance. From the time of Moses we find Ephraim and Manasseh giving their names to tribes (Numbers 1), which received territory on the conquest of Canaan.