The 39-year-old son of Natalie Cole and grandson of Nat King Cole, Robert Yancy, was found in his San Fernando, California, apartment on Monday night. A concerned friend found his body after he was not heard from for several days.

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TMZ reports that family members were informed of Yancy's death around 2:30 a.m. on Tuesday morning.

Investigators believe Yancy died of a heart attack, according to his family. His death has been listed as natural, pending an official autopsy and toxicology report. The family believes that drugs were not involved.

Yancy’s mother, Natalie Cole, struggled with drugs in her lifetime before her 2015 death. Her official cause of death was congestive heart failure.

Yancy’s family insists that he did not have a drug problem and said he was “turning his life around” while working in the music industry.

His father, pastor and gospel musician Marvin Yancy,  died of a heart attack at the age of 34.

Natalie Cole and Marvin Yancy were married from 1976 to 1980.

Robert Yancy, Natalie Cole and Felanice Yancy attend Natalie Cole's 60th Birthday Party on February 1, 2010 in Beverly Hills, California.  (Photo by Duffy-Marie Arnoult/Getty Images)

Credit: Duffy-Marie Arnoult

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Credit: Duffy-Marie Arnoult