But that relationship became strained after Ronald Goldman and Nicole Brown Simpson, who had divorced the retired football star, were both found slain in Los Angeles June 12, 1994.
Though Simpson was eventually acquitted on criminal murder charges, Jenner said Nicole Brown Simpson had often predicted her own demise at the hands of the Hall of Famer.
Jenner’s interview reflecting on the tragic events two decades ago will be featured in a new LMN documentary called "The Secret Tapes of the O.J. Case: The Untold Story," which premieres Sept. 30 at 8 p.m. ET. The A&E documentary, “O.J. Speaks: The Hidden Tapes,” premieres Oct. 1 at 9 p.m. ET. (Both A&E and LMN are partly owned by ABC News' parent company, Disney.)
“At the end of Nicole's life, I think she finally was at a place where she knew she had to be more vocal with what was going on and she was in trouble,” Jenner told LMN about Nicole and O.J. Simpson’s tumultuous relationship. “The one thing she would tell all of us by the time, you know, it got to that level was, ‘He's going to kill me and he's going to get away with it.’
"I will always feel guilty that I didn't pay more attention and didn't speak up when I thought anything was wrong or asked her more, 'Do you want to talk about it?'" Jenner said.
She also had to listen to a police call, played as evidence, that was a cry for help from Nicole Brown Simpson the October prior to her death. In the call, she claims O.J. is “going nuts” and is “going to beat the s*** out of me,” Jenner said.
“Her voice, pleading for somebody to come to her house because she thought he was going to beat the s*** out of her, you know, I think that, that was so shocking to me because I had never heard that before.”
Jenner said she and her ex-husband didn’t talk about the trial, just the children they shared.
“Our opinions are so obviously black and white,” she said of her and the famed attorney. “What good is it going to do?”
Jenner did admit back then to speaking with O.J. Simpson a few times from jail.
“I didn’t do it,” is what she said the football star claimed over the phone.
In the documentary, Jenner put herself back in that time period and in that courtroom. She remembers looking at her ex and the father of her children when the verdict came back, “Not guilty.”
“I think he was shocked,” she said of Robert Kardashian. “He was definitely stunned. I mean you could look at his face and see it. I've known him my entire life. I know that like he was ... he was floored that that was the verdict.”
Eventually, Robert Kardashian’s relationship with Simpson soured, as well, and even as his life was ending, Kardashian didn’t reconnect with his one-time friend. He later died from cancer in 2003 at age 59.
“O.J. did try to reach out and call him,” Jenner said, “but Robert didn't take the call.”