In 1986, tragedy struck Heigl, then 7, and her family when Jason was thrown from the back of a pickup truck and suffered life-threatening brain injuries.

The teen was rushed to a hospital where doctors desperately tried to save his life in an eight hour operation. But it was in vain. Doctors finally had to give the family the shattering news - Jason was brain-dead.

"The days surrounding Jason’s accident were incredibly difficult for Katherine and her family," a friend of the star tells GLOBE. "Jason was Katherine’s older brother and she idolized him."

"They all loved Jason so much. It was as if a part of them died that day."

The Heigl’s made the difficult decision to donate Jason’s organs to help save others, which they knew Jason would have wanted.

"Katherine and the rest of her family knew what a good person he was," the friend continues. "He would have done anything to help other people."

Later, Heigl and her mom appeared on an episode of Crossing Over with John Edward, the psychic who tries to help families contact loved ones from beyond the grave.

Now, the 26-year-old former model uses her celebrity status to promote the importance of organ donation.

"It’s hard for people to be thinking about organ donation for the first time in the midst of a crisis," says Katherine.