The New Edition star has opened up about the former couple's turbulent relationship in his new memoir, Every Little Step, in which Bobby recalls the first time he saw the late R&B superstar take an illegal substance.

The singer confesses he broke wedding traditions by checking in on his bride before they exchanged vows, but was "shocked" to find Whitney "hunched over a bureau snorting a line of coke".

She claimed she was taking a hit to calm her nerves and allegedly invited Bobby to join her, but he declined.

Bobby has since discussed the incident further in a candid chat with U.S. newswoman Robin Roberts, whose interview will air on 20/20 on Tuesday night (07Jun16).

"The drugs wasn't her (sic)," he says, growing emotional. "She did drugs but drugs didn't do her. She knew how to handle herself. It only made me love and want to protect her more."

Brown also battled substance abuse during their marriage, but he has long maintained hard drugs were a part of Whitney's life before they became romantically involved, and he goes on to underline the fact in his 20/20 interview.

"It wasn't me who started her (on drugs)," the My Prerogative hitmaker states. "I take my part and I take it hard for me even being a part of it, but we all have our own minds and some of us are stronger than others."

Whitney continued to struggle with drugs following their divorce in 2007, and cocaine was also listed as a contributing factor in her accidental drowning death in 2012, when she was found dead in a bathtub in her suite at the Beverly Hilton Hotel.

Ironically, the former couple's only child, Bobbi Kristina, was also discovered unresponsive in the bath at her Georgia home in January, 2015. She was placed in a medically-induced coma, but she never recovered and passed away in July (15), aged 22.

Heartbroken Brown is convinced his daughter's boyfriend Nick Gordon, who was informally adopted by Whitney as a child, knows more about the deaths of both Bobbi Kristina and her mother.

Fighting back tears in the 20/20 news special, he claims, "The same thing that happened to my daughter is what happened to Whitney. There was only one person who was around on both occasions... I won't say his name... He knows what happened. I don't know what happened that night, but he does."

Gordon's lawyer has since slammed the allegations as "baseless".

Brown's revealing TV interview will air a month after he joined his daughter's court-appointed conservator, Bedelia Hargrove, as a plaintiff in the wrongful death civil case against Gordon.