Bobby Brown Opens Up About Nick Gordon and His Suspicions Surrounding Bobbi Kristina and Whitney

For the first time since the death of Bobbi Kristina Brown last July, Bobby Brown sits down to talk about his suspicions towards his daughter's boyfriend Nick Gordon.

In a 20/20 interview with Robin Roberts, airing on Tuesday on ABC, Brown addresses the fact that Gordon was present when both his ex-wife, Whitney Houston, and their daughter were found unresponsive in bathtubs.

WATCH: Bobbi Kristina Brown Died From Drug Intoxication, Immersion in Water, Medical Examiner Says

Houston -- who was married to Brown for 15 years -- died in 2012 at the age of 48 after she was found unresponsive in a bathtub at the Beverly Hilton. Three years later, Bobbi Kristina died six months after she too was found unresponsive in a bathtub in her Georgia home. She was 22.

"It's not a mystery to me- the same thing that happened to my daughter is what happened to Whitney," Brown tells Roberts. "There is only one person that was around both occasions."

EXCLUSIVE: Pat Houston Opens Up for the First Time About Bobbi Kristina Brown's Death

When Roberts asks Brown to confirm he's talking about Gordon, he responds, "I won't say his name."

"Nick Gordon, the things that are being said by him recently, how do you approach that?" Roberts asks.

WATCH: Bobbi Kristina Brown Used Heroin, Smoked Marijuana and Crack 'Often,' According to Friend's Deposition

"He knows what happened," Brown answers. "I don't know what happened that night but he does."

In April, Gordon spoke with Dr. Phil about discovering his girlfriend unconscious, and how similar the situation was to the death of Bobbi Kristina's mother three years earlier. "It was literally a nightmare all over again," he said.

Gordon told Dr. Phil that he used drugs "socially" with Bobbi Kristina while Houston was still alive, but claimed that her drug use "got really bad" after the singer's death. "At the time, that's kind of the only way we knew how to deal with what had happened," he added.

WATCH: Nick Gordon Wishes Bobbi Kristina Brown a Happy Birthday, Responds to Release of Her Autopsy

Gordon is in an ongoing $10 million wrongful death civil lawsuit filed last October by Bobbi Kristina's conservator, Bedelia C. Hargrove. The lawsuit alleges that "Ms. Brown died due to a violent altercation with Defendant (Gordon) after which he placed her in a bathtub, unconscious, after [Gordon] injected her with a toxic mixture."

"I look forward to having the Court hear the evidence in the civil lawsuit and hopefully the criminal action very soon," Brown said in a statement.

No criminal charges have been filed against Gordon and his lawyers have called the wrongful death civil suit "slanderous and meritless."

WATCH: Bobby Brown Breaks Down Talking About Daughter Bobbi Kristina's Death -- 'My Baby's Gone'