For over 35 years, A-list Hollywood actress Katherine Heigl has remained quiet on the details and impact of her brother Jason’s tragic death. That is until recently.

The A-list Hollywood actress opened up about the experience of losing a sibling so young in a moving tribute posted to her Instagram and Facebook.

"This is my brother Jason. He was about 12 or 13 in this picture. He was taken off life support 35 years ago today," Heigl shared with her over four million followers.

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On September 23 1986, Jason was involved in a tragic car accident that led him to the ICU, where he was on life support for seven days. He died one week before his 16th birthday.

"I don’t often talk about him. Or this day. Or the weeks and months and years that followed, but my mother wrote an email to a friend this morning that she shared with me and I thought… well that I’d like to share her words because what she has to say is important. Not only for my family but for anyone out there who has lost someone they love too soon.

"[From Nancy Heigl] – actually, today is the day that he died in 1986. All day today, various helicopters flew into Norwalk Hospital in Connecticut, bringing surgeons from other hospitals and early this evening they took him into surgery and removed his organs for donations. Sorry, just on my mind today and probably sharing too much."

It was a heartbreaking decision for her parents, Heigl notes, but a decision the family knew Jason would approve.

"They donated his eyes. His heart. His lungs. They donated what they could because they not only knew it was what Jason would have wanted but because they did not want anyone else to suffer what they now would have to if they could prevent it.

"My mother always says it was not the easy thing to do but it was the right thing to do."

Nancy has a house on her daughter’s sprawling estate ranch in Utah, where they keep horses, donkeys, goats and chickens.

The ranch also includes ‘Heigl Hounds of Hope’ – an adoption centre for vulnerable dogs rescued from high-kill shelters. The centre is supported by the Jason Debus Heigl Foundation, a not-for-profit the Heigl family established in honour of Jason.

It’s a cause that was close to his heart, Heigl tells: “Jason influenced our family in every way possible. He was always looking out for and caring for the voiceless and the innocent,” she said in an interview with Dogster.

"He really especially loved a big black Labrador we had named Ben Davis. When Jason was hospitalised for the week after his accident and died, Ben Davis ran away, and we all thought he was out looking for Jason. Finally, after about five days, we found him and brought him home. I believe he knew Jason was gone and [the dog] missed him the whole rest of his life."

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The Firefly Lane,Grey’s Anatomyand27 Dressesactress has spoken previously about how her loved ones and family are her first priority. Heigl and her partner of 14 years, musician Josh Kelley, are parents to two adopted children, Naleigh and Adalaide, and one biological son, Joshua Jr.