Manasses means "causing to forget."   Manasses was not one of Jacob's sons, he was Jacob's grandson. Manasses's father was Joseph, who was Jacob's favorite son. Joseph was the son that was sold to Egypt as a slave by his brothers.

On Jacob's deathbed he told Joseph that his two sons were now Jacob's sons as it is written.

Gen 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.

Everything that happen to Flesh Israel happened as an example to the believers and followers of Jesus Christ which is spiritual Israel. From this we learn that there is an adoption of others in the plan of God. That these others would be born while they were in bondage and the Lord will still accept them as equal as it is written.

Gal 4:3    Even so we, when we were children, were in bondage under the elements of the world:
4    But when the fulness of the time was come, God sent forth his Son, made of a woman, made under the law,
5    To redeem them that were under the law, that we might receive the adoption of sons.
6    And because ye are sons, God hath sent forth the Spirit of his Son into your hearts, crying, Abba, Father.


IHS