“It’s very important for Katherine to include her brother in a meaningful way at her wedding,�? a friend tells Star. “The ceremony is still in its formative stages, but she has talked about having a single candle- which will embody Jason’s spirit- placed next to her and Josh while they exchange their vows. She may also address her brother during her remarks at the reception. If anything will make her break down and cry, I’m sure that will be it.�?

On Sept. 30, 1986, 15-year-old Jason died from massive injuries he sustained after he was thrown from a pickup truck seven days earlier in New Canaan, Conn. Katherine was just 7 years old at the time.

One positive thing emerged out of this tragedy: “When we realized he wasn’t going to survive, the family decided it was important to donate his organs,�? Katherine’s mom, Nancy Heigl, told Star in 2005. “Jason’s heart, kidneys and eyes were given- whatever could be used by someone in need. It was Jason’s last gift to a world he had the greatest affection for.�?

Katherine said: “What [my mother] went through, losing a child, was so horrible and devastating that she couldn’t imagine sitting idly by if she had the opportunity to save another mother from having to go through it. And Jason was someone who was so beautifully alive and passionate about life. It was clearly what he would have wanted.�?

Now promoting organ donation is a driving force in Katherine’s life. “I learned through a difficult experience that this is the right and humanitarian thing to do,�? says Heigl. “It’s the most honorable way to preserve the memory of someone you love.�?

Someone else the sexy TV star loves, of course, is her husband-to-be singer-songwriter Josh Kelley, 27. The couple met in 2005, when Heigl was cast in the music video for his single, “Only You,�? shot in L.A.’s Venice Beach neighborhood.

“The video is about these two people flirting through their apartment windows- and we were flirting for real,�? Katherine, 28, recalls. And when Josh popped the question in June 2006, he had a special surprise in store! “[We] went back to the place where we shot the video,�? says Kelley. “It was dark, and I had set up a table with a nice white tablecloth and roses, wine, chocolate cake, the music we listened to when we first started dating…everything! And then, when she had this mouthful of cake, I was like, ‘Will you marry me?’ She said yes, and we walked down to the beach. It turned out better than I actually had imagined!�?