Genesis 46:27

and the sons of Joseph which were born him in Egypt were two souls; all the souls of the house of Jacob which came into Egypt were three-score and ten. Note that this enumeration is made according to the custom which listed the founders of families in such a table, even though some of them were not yet born. Cf Exodus 1:5; Deuteronomy 10:22. In addition to the twelve sons of Jacob, who were the founders of the twelve tribes, all those grandsons and great-grandsons are listed who became the ancestors of independent families with large numbers and great influence. In the account of Stephen, Acts 7:14, three grandsons and two great-grandsons of Joseph are included, for this reason. "Thus only can the fact be explained, otherwise inexplicable, that in the days of Moses, with the exception of the double tribe of Joseph, there were, in none of the tribes, descendants from any son or great-grandsons of Jacob that are not mentioned in this list. " The names here given represent the nucleus from which the children of Israel, the great nation, grew.