The allegations surfaced in Kevin Macdonald's new documentary, "Whitney," which premiered Thursday at the Cannes Film Festival. Warwick, who was also a singer, was 18 years older than Houston and died in 2008.
According to The Hollywood Reporter, Mary Jones -- Houston's longtime assistant -- told Macdonald in the film that she learned of the molestation from Houston herself. Houston's brother, Gary Garland-Houston, also told Macdonald he was molested by a female family member when he was between the ages of 7 and 9. He said his sister was abused, too.
The molestation allegations made in "Whitney" only add more sadness to the troubled life of Houston. According to Jones, the experience with Warwick made the singer question her sexuality and contributed to her addiction issues later on in life.
Houston died in 2012 at the age of 48 from what was ruled an accidental drowning in a bathtub at her home. A coroner's report on her death cited heart disease and drug use as contributing factors, though she never spoke publicly about her alleged drug abuse.