Is Mary Cosby Related to Bill Cosby? Why Mary and Bill Aren’t Family”

Mary Cosby is a prominent figure on the reality TV show “The Real Housewives of Salt Lake City (RHOSLC),” which made its debut in 2020. She is celebrated for her opulent lifestyle, her role as a Pentecostal preacher, and her controversial marriage to her late grandmother’s second spouse, Robert Cosby Sr.

In contrast, Bill Cosby is a renowned comedian, actor, spokesperson, and media personality, who has made substantial contributions to both American and African-American culture. He is most recognized for his portrayal of Cliff Huxtable on “The Cosby Show” (1984-1992), earning him the affectionate nickname “America’s Dad.” However, his career was marred by allegations of sexual assault from numerous women, and his conviction was overturned in 2021.

Given their shared last name and involvement in the entertainment industry, many have speculated about a possible familial connection between Mary and Bill. Nonetheless, there is no factual basis to support such a claim, as the following points illustrate:

Different Origins

Mary and Bill hail from distinct geographical and socio-cultural backgrounds. Mary was born in 1972 in Utah, United States, as the granddaughter of Dr. Rosemary Redmon “Mama” Cosby, the founder of the Faith Temple Pentecostal Church in Salt Lake City. Her inheritance of her grandmother’s fortune and church occurred after her marriage to Robert Cosby Sr., who was Mama’s second husband and her step-grandfather.

On the other hand, Bill Cosby was born in 1937 in Philadelphia, Pennsylvania, United States. He is the son of William Henry Cosby Sr., a US Navy sailor, and Anna Pearl Hite, a maid. His upbringing occurred in a modest family, leading him to drop out of high school and join the Navy. His eventual path led to a career in comedy and acting, where he achieved immense success and influence.

Different DNA

Mary and Bill have distinctive DNA profiles and ancestral heritage. Mary’s heritage is primarily African-American, with some Native American and European ancestry. While she hasn’t publicly disclosed her DNA test results or family tree, she takes pride in her heritage and identity.

Bill Cosby also has African-American roots, coupled with some Irish ancestry. He has openly shared his DNA test results and family lineage, revealing connections to notable figures in African-American history, such as Booker T. Washington and Richard Allen. Additionally, he has traced his paternal lineage to Cameroon and his maternal lineage to Benin.

Different Surnames

The last names of Mary and Bill Cosby are associated with distinct historical origins. Mary’s surname, Cosby, is the result of her marriage to Robert Cosby Sr., who was her grandmother’s second spouse. The Cosby surname can be traced back to an English occupational name for someone involved in constructing or selling cottages or huts, likely stemming from white settlers who arrived in America from England or Ireland.

In contrast, Bill Cosby’s last name, Cosby, is inherited from his father, William Henry Cosby Sr., who was born in Virginia in 1910. Similarly, William’s surname is linked to the English occupational name but with a different historical context. In this case, the ancestors were most likely enslaved Africans brought to America by white slave owners who assigned them their surnames.


In summary, there is no familial or marital connection between Mary Cosby and Bill Cosby. Their dissimilar origins, backgrounds, DNA, ancestry, and surnames clearly demonstrate their lack of any biological or legal ties. While both are notable figures in their respective fields of entertainment, their sole commonality lies in sharing the surname “Cosby,” which they obtained through separate and unrelated circumstances.

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