ABC/ Rick RowellContrary to popular belief, it wasn’t Bobby Brown who sparked Whitney Houston‘s drug habit. That’s just one of many revelations in tonight’s special edition of 20/20, in which ABC’s Robin Roberts sits down for an exclusive interview with the singer who Whitney herself referred to as “The King of R&B.”

“I didn’t expect him to be so revealing, to open up as much as he did so freely,” Roberts told ABC Radio.

Brown talks to Roberts about his journey from New Edition, to his chart-topping solo career, to his marriage to the late Whitney Houston – all topics featured in his new memoir, Every Little Step, which hits stores June 13.

One of many revelations Brown discusses with Roberts is the first time he witnessed Whitney doing cocaine: on their wedding day.

“Oh, yeah, the wedding … [he] wanted to see her beforehand, walked in and she was doing a line of coke,” Roberts said.

In an advance clip of the interview, Brown says that despite that incident, he didn’t feel that Whitney had a drug problem. “She knew how to handle herself. It only made me want to love and protect her more,” he says.

Brown, who’s now married and expecting his third child with wife Alicia Etheredge-Brown, continues to deal with his own substance abuse.

“He has not been involved with ‘narcotics’ — that’s how he phrases it — for at least 10 years, but…he struggles staying sober when it comes to alcohol, and every now and then he has to, in his words, ‘reboot,’” Roberts said.

She added that Brown seems to want to turn over a new leaf.

“I just really sense from him that owning up to, ‘Yes, I was the bad boy of R&B, alright, and some of it was true, some of it was not,'” she told ABC Radio. But now, she says, “He has a lot of reasons to stay clean.”

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