Ron Goldman's sister speaks out 25 years after his murder

In the 25 years since the murders of Ron Goldman and Nicole Brown Simpson, Goldman’s sister has always marked the anniversary in silence -- but this year she’s speaking out for the first time.

"I usually reserve the peace and quiet of the day to myself," Kim Goldman told ABC News. "This is the year of confronting."

Watch "Good Morning America" on Wednesday, June 12, at 7 a.m. ET for an exclusive interview with Kim and Fred Goldman.

June 12, 1994, is when Kim Goldman's life forever changed. Her older brother, 25-year-old Ron Goldman, was returning a pair of glasses to Brown Simpson's Los Angeles home when the two were attacked and brutally stabbed to death.

"He put himself in harm's way to protect somebody else," said Kim Goldman. "His last act of his life really showed you exactly who he was -- his dedication and his commitment to his friends and the people that he loved and cared about. Even Nicole, for all we know who was an acquaintance. He didn't run."

Brown Simpson's ex-husband, former NFL star O.J. Simpson, went to trial for the double murder and was acquitted of all criminal charges. A civil jury in 1997 found him liable for wrongful death and he was ordered to pay millions to the families.

In 2008, Simpson was convicted in a botched robbery and sent to a Nevada prison. Simpson was released in 2017 and now lives in Las Vegas.

Kim Goldman on Wednesday is launching a 10-episode podcast called "Confronting: O.J. Simpson." In the series she interviews key members of the case, from prosecutor Marcia Clark to Simpson house guest Kato Kaelin.

On the podcast Kaelin recalled a conversation he said he had with Simpson after the crime.

"O.J. pulled me into the kitchen by himself and said, 'You know I was here with you.' And I said, 'No, I don't,'" Kaelin said. "I was like, 'Is he trying to use me for something I think he could've done?'"

For Kim Goldman, the podcast is an outlet to pose questions that have haunted her for years.

"There's been so much coverage," she said, but also "a lot of missed opportunities, I think, to ask questions that go a little bit beyond the more obvious."

"For me to be able to sit down with people I've had such a profound relationship with, or have been connected to for so long, seems like a great way to go a little bit deeper," she said. "I'm proud of how far I've come and my dad has come. I'm proud of the growth and resiliency and the courage."

This year is an especially poignant anniversary for the Goldmans. Ron Goldman was 25 years old when he was killed; now he's been gone as long as he was alive.

"He would be 50," she said. "It's really hard to kind of wrap my head around who he would have become. Those are ... realizations that are really hard for me, because they'll never be."

"I can't argue with my brother," she said of his absence. "I can't introduce him to my son.”

Kim Goldman says she's told her 15-year-old son about how his uncle was killed, though she left out "the brutality" of the crime.

"He knows that my brother died a hero. He knows that my brother was my best friend," she said. "And I share as many stories of him as I can."

Twenty-five years after suffering tragedy in the spotlight, Kim Goldman aims to honor her brother through her work as a victims' advocate. She lends her voice to advocating for issues including gun control, statute of limitations on sexual assault, and teen mental health. She also serves as a Vice Chair for the National Center for Victims of Crime, where she works on policy and victims' access to resources.

Though life moves on, Kim Goldman says the hardest weeks of each year are from June 12 -- the anniversary of her brother's death -- through July 2, his birthday.

"No matter what I try to do on June 12, my body is just in tune with time and knowing what my brother did all day long and how the timeline played out," she explained. "Your body just remembers, it absorbs the trauma and no matter what you try to do, it stays with you."

Overcome with emotion, Kim Goldman said her message to others is to "hold dearly the people you love and care about, and not take it for granted."

"I'm very fortunate my brother and I were tight. He always knew how much I loved him. But in a second, someone can be taken from you," she said. "I know how fragile life can be. My brother unfortunately taught me that."