Regarding Patriarchal blessings and the declaration of lineage, President James E. Faust stated:
The Church is expanding at a tremendous rate. We now have stakes of Zion in a great many countries of the world, and most stakes have at least one patriarch. This growth permits many people across the earth the privilege of receiving patriarchal blessings. As President Joseph Fielding Smith stated, “The great majority of those who become members of the Church are literal descendants of Abraham through Ephraim, son of Joseph”(Doctrines of Salvation, 3:246). However, Manasseh, the other son of Joseph, as well as the other sons of Jacob, has many descendants in the Church. There may be some come into the Church in our day who are not of Jacob’s blood lineage. No one need assume that he or she will be denied any blessing by reason of not being of the blood lineage of Israel. The Lord told Abraham, “And I will bless them through thy name; for as many as receive this Gospel shall be called after thy name, and shall be accounted thy seed, and shall rise up and bless thee, as their father.” (Abraham 2:10)
Nephi tells us that “as many of the Gentiles as will repent are the covenant people of the Lord.”(2 Nephi 30:2) Therefore it makes no difference if the blessings of the house of Israel come by lineage or by adoption.
Some might be disturbed because members of the same family have blessings declaring them to be of a different lineage. A few families are of a mixed lineage. We believe that the house of Israel today constitutes a large measure of the human family. Because the tribes have intermixed one with another, one child may be declared to be from the tribe of Ephraim and another of the same family from Manasseh or one of the other tribes. The blessing of one tribe, therefore, may be dominant in one child, and the blessing of another tribe dominant in yet another child. So children from the same parents could receive the blessings of different tribes. (Conference Report, Oct. 1995, 83; or Ensign, Nov. 1995, p. 64)