Natalie Cole's Son, Robert Yancy, Has Died at 39.

The only child of Natalie Cole, daughter of the legendary singer Nat King Cole, was found dead in his apartment on Monday. The body of Robert Yancy, who was only 39, was found in his California apartment by a close friend who went to check up on him after not having heard from him in a few days.

Via TMZ:

Family members tell us ... authorities contacted them at 2:30 AM Tuesday and said Robert died of a heart attack. Law enforcement tells us, pending an autopsy, they have listed it as death from natural causes, but that can change once the autopsy and toxicology tests are completed.

The family tells us authorities were clear to them, drugs were not involved. As you know, Natalie famously fought drug addiction throughout her adult life until her 2015 death. Her cause of death was congestive heart failure.

Family members say Robert -- the grandson of Nat King Cole -- had never abused drugs and was "turning his life around." He worked in the music industry.

Robert's dad died of a heart attack at age 34, so it could be heart disease runs in the family.

This is why it's so important to check up on your friends. May he rest in peace with his mother.