Nicole Brown Simpson's Sisters Question if More 'Could Have Been Done' to Save Her

Nicole Brown Simpson was murdered in June 1994.MEGA

Nearly 30 years after Nicole Brown Simpson's murder, her siblings opened up about her life and death — and questioned if there was more they could have done to potentially save her, RadarOnline.com has learned.

Denise, Dominque and Tanya Brown sat down with Diane Sawyer ahead of the upcoming Lifetime documentary, The Life & Murder of Nicole Brown Simpson.

Nicole and O.J. were married from 1985 to 1992. MEGA

During their interview with Sawyer, Nicole's sisters confessed they still struggle with grief — and processing the death of her ex-husband and accused murderer, O.J. Simpson, has been "complicated."

While O.J. was criminally acquitted of the murders of Nicole and her friend, Ron Goldman, the Brown siblings believe he was responsible.

Nicole's sisters sat down with Diane Sawyer ahead of the release of Lifetime documentary 'The Life & Murder of Nicole Brown Simpson.'ABC NEWS

Dominque reflected on a time when Nicole confided in her about a violent incident with O.J. — and admitted she didn't handle the conversation the right way.

"I asked her all the 'whys' that you don't ask. ... 'Why don't you just get out of this relationship? Why don't you just leave him?" Dominque recalled, according to ABC News. "Those are things that you don't say, and I didn't realize that at the time."

The history of abuse in Nicole and O.J.'s relationship has been well-documented. At the time of her death, Nicole and O.J. were divorced, however, the ex-NFL star was said to still be exhibiting controlling behavior over his ex-wife.

"I just wish that I had known more," Dominque said. "I just wonder if I could have done more to help or to listen to her."

O.J. was acquitted of Nicole and Ron Goldman's murders in 1995. MEGA

Since their sister's murder, Dominque, Tanya and Denise have advocated for strengthening domestic violence laws, including the Violence Against Women Act.

"I sit there and I go, 'Why did it have to take my sister?'" Denise said. "Why did it have to take Nicole for people to understand that domestic violence can kill?"

Denise later noted that when she learned O.J., who maintained his innocence until his death in April, passed away from cancer, she recalled, "I felt, like, this sense of kind of relief in a way."

The sisters noted that O.J.'s death was "complicated" because of their relationships with Nicole and O.J.'s children, Sydney and Justin.

Denise dismissed possible CTE as an explanation for O.J.'s abuse. ABC NEWS

"It's very complicated. But I have a relationship with the kids that means everything to me, and I was ... very, very sad for them," Dominque explained.

The sisters also discussed the possibility of CTE from O.J.'s football career playing a role in their sister's abuse.

"I had a conversation with Leigh Steinberg, the sports agent," Tanya said. "And he was talking about, 'There could have been a TBI, traumatic brain injury [with Simpson.]' And I said, 'No. Possibly, but, when you know the person's character and what he's capable of, yeah, that's not.. that's.. that's violence, that's power and control."