Genesis 48:5

And now thy two sons, Ephraim and Manasseh, which were born unto thee in the land of Egypt before I came unto thee into Egypt, are mine; as Reuben and Simeon they shall be mine. It is significant that in this formal statement of adoption the name of Ephraim is set before that of Manasseh, the birthright thus being changed. The divine blessing of promise, of which Jacob was the bearer, empowered him to adopt these two grandsons and to give them equal rights with his oldest sons, designate their descendants as two fully recognized tribes among the children of Israel.