Joseph Fielding Smith states that patriarchal blessings of Black Saints should declare them to be of the lineage of Cain or Canaan.
Joseph Fielding Smith, Jr. 1957-1966. Answers to Gospel Questions. 5 vols. (Salt Lake City, UT: Deseret Book, 1979), 5:168
Can a Person Go to the Temple without Knowledge of His Genealogy?
Question: "When a person is converted and accepts the gospel and is baptized a member of the Church, without any information regarding his genealogy, can he be ordained into the priesthood? Can a woman in similar circumstances obtain a recommend to go to the temple of our Lord to receive her endowments or become married for time and eternity?"
Answer: When a person is baptized and confirmed and receives the priesthood and is worthy he may go to the temple and be married for time and all eternity. We do not question his genealogy, except that he is white. Those who have the blood of Cain do not go to the temple for endowment. Every person should prove himself worthy before going to the temple.
Negroes May Have Patriarchal Blessings
A Negro may have a patriarchal blessing, but it would declare him to be of the lineage of Cain or Canaan.
The covenants and blessings of the lineage of Joseph are the same as the blessings given to anyone else who repents and receives the gospel, which is through their faithfulness in the Father's kingdom.