Nicole Brown's sisters reveal their 'complicated' reaction to OJ Simpson's death

Nicole Brown Simpson's sisters have sat down for an interview with Diane Sawyer a little over a month after OJ's death, which they said they have mixed feelings about.

The trio - Tanya, Dominique, and Denise - revealed how they felt about the former football player's death at the age of 76 in his Las Vegas home, and told the ABC News anchor about some of the questions left unanswered surrounding Nicole's death.

This ranged from why their sister never left him, and whether the one-time Buffalo Bills running back suffered from chronic traumatic encephalopathy - better known as CTE.

When asked, they said Simpson's rage was to blame for the fatal stabbing - something they said they could have been avoided if they handled the situation differently.

Brown Simpson went on to be brutally stabbed outside her LA home on June, 15, 1995. Simpson was famously acquitted in the case surrounding not only her murder, but that of her friend Ronald Goldman, who was at the home at the time.

Scroll down for video: 

Denise, Dominique, Tanya Brown sat down with Diane Sawyer Tuesday on Good Morning America for a tell-all interview

Next month marks the 30-year anniversary of Brown Simpson's murder, for which her husband OJ was famously acquitted

'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?"' Denise Brown, 66, tearfully recalled of the alleged domestic abuse she said led to the murder.

'Those are things that you don't say, and I didn't realize that at the time.'

'I just wish that I had known more,' Dominique, 56, added, visibly emotional.

'I just wonder if I could have done more to help or to listen to her.'

Denise, a fierce advocate for stricter domestic abuse laws, claimed her younger sister even once confided her about a violent blowup with Simpson - but still stayed.

'I sit there and I go, "Why did it have to take my sister?"' she said, referring to domestic household abuse. 

'Why did it have to take Nicole for people to understand that domestic violence can kill?'

Sawyer, 78, sat attentive as the sisters spoke, pointing out how next month marks 30 years since the night of Nicole's murder.

The conversation at one point steered to CTE - a condition some have theorized could have been a contributing factor in the case. OJ spent 11 seasons in the famously physical National Football League (NFL).

From the last Brown family photo, take on Mother's Day 1994. It shows from left to right, Denise, Nicole, Dominique, mother Juditha, and youngest Tanya

On Tuesday, 54-year-old Tanya (at far right), ruled out that CTE played a factor in OJ's actions that night in June 1995 - citing a conversation with a well-known sports agent

Denise, a fierce advocate for stricter domestic abuse laws, claimed her younger sister once confided her about a violent blowup with Simpson, but still stayed with him. 'I just wish that I had known more,' Dominique added. 'I just wonder if I could have done more to help'

Tanya, Denise, and Nicole during their younger days, around the time she was working as a waitress, planning to study photography, and met her future husband

'I had a conversation with Leigh Steinberg, the sports agent,' youngest sister Tayna, 54, said on the subject.

'And he was talking about, "There could have been a TBI, traumatic brain injury [with Simpson.]"

'And I said, "No," the concluded, citing Simpson's supposed mercurial attitude.

'Possibly,' she conceded, '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.'

Simpson was eventually arrested for double murder, and put on trial for the murders of both Nicole and Goldman. 

In October of that year, he was acquitted of all criminal charges, though in 1997, a civil jury found the football star liable for wrongful death.

Following Nicole's death, Dominique said she found her personal handwritten diaries which detailed many of the times OJ had physically beaten her and the injuries he had inflicted upon her. 

The conversation at one point steered to CTE - a condition some have theorized could have been a contributing factor in the case. OJ spent 11 seasons in the famously physical National Football League (NFL), primarily for the Buffalo Bills

Simpson shows the jury a new pair of Aris extra-large gloves, similar to the gloves found at the LA crime scene during his double murder trial, which has inspired controversy

'I found her will, her diaries, just stacked in a box underneath the kitchen cabinet with the kid's artwork and bunch of other stuff,' Dominique told Sawyer during the sitdown.

At a point, Denise, the eldest sister interjected: 'She was trying to hide it.'

She went on to detail how OJ's abuse started with Nicole, recalling how the sports star would commonly say to their sister: '"You're stupid, you're ugly, you're fat, you're worthless, nobody's gonna want you, I'm the only one who can put up with you"

'That escalates into that physical violence, and that's the hitting, the kicking, the punching,' she said.

She went on to allege that she once found a Polaroid photo of Nicole with a black eye, and when she questioned her sister about it, she lied and said it had been done by a makeup artist.

'I said, "Oh my God, Nic look at that black eye!" Denise said, growing animated at points.

'"No, no, it was the makeup artist at the studio,"' she credited her sister as saying.

'I said, "oh my god, it looks so real," and I threw it right back in the drawer. I didn't know it was a real black eye, I had no idea.

When asked how they felt about his death, they said they had conflicting feelings - citing how Nicole's now grown children with OJ are now without both a mother and a father. Sydney, 38, and Justin, 35, were just eight and five, respectively, when their mother was killed 

When asked how they felt about his death, they said they had conflicting feelings - citing how Nicole's now grown children with OJ are now without both a mother and a father. 

Sydney, 38, and Justin, 35, were just eight and five, respectively, when their mother was killed - something the sisters appeared not willing to forgive.

'It's very complicated,' Dominique, the only sister to reply, said. 'But I have a relationship with the kids that means everything to me, and I was ... very, very sad for them.'

When asked how they had coped with '30 years of rage and heartbreak,' Tanya added: 'A lot of therapy. It was rough, unresolved grief, everything bit me hard ten years later,'   

Middle child Dominique, meanwhile, recalled: 'Sometimes I would think, "gosh, I am just staggeringly sad today".

'And I would realize that it was the day she was murdered, or it was her birthday, or something or some memory would come up.

Eldest sister Denise concluded: 'The pain doesn't go away, it doesn't subside, it doesn't get easier. But you do the best you can, and you move on and it's one step forward.'