The right hand was for the head of the firstborn, and Jacob was deliberately giving that position to the younger son. That pattern was followed for four consecutive generations:
Isaac over Ishmael,
Jacob over Esau,
Joseph over Reuben, and
Ephraim over Manasseh.
Many years later, Ephraim became the leading tribe in the northern kingdom, superior to the tribe of Manasseh. The entire northern kingdom of Israel was occasionally called Ephraim (see study notes on 2 Chronicles 28:12; Isaiah 11:13; Ezekiel 37:15–28; Hosea 6:4; Zechariah 9:10).