"The hardest thing I've ever had to do in my life was to tell my daughter to let go," he said.
In this preview Brown, still grief stricken, notes that his daughter and his ex-wife died in tragically similar ways.
"There's only one person who was around both occasions," Brown said.
"Nick Gordon is who you're referring to," Roberts responded, noting the wrongful death lawsuit filed by Bobbi Kristina's estate.
Gordon's legal team has blasted the lawsuit as slanderous and meritless.
alleges financial impropriety and severe physical harm
"He knows what happened," Brown said. "I don't know what happened that night, but he does."
In March, Gordon's legal team issued a statement saying her death was “was an accident… or even a suicide, but not a murder,” and sought an end to the specter of possible legal or criminal proceedings involving him.
The lawsuit was filed when Bobbi Kristina was still alive and amended after her death. Gordon’s legal team responded
seeking a dismissal on numerous grounds
– namely that the suit against him lists damning allegations but no police reports, affidavits or other backing evidence.
No charges have been filed against anyone in connection to Bobbi Kristina's death.
Here's the "20/20" preview: