Pasadena, California (CNN) -- A tender smile frames the face of Eva Perez as she remembers the life of her 6-year old son.
"Hernan was a very happy boy," she says. "He gave me flowers all the time. He's the first 'man' (to) give me flowers."
But her smile is thinly veiled -- her face splintering into tears as she permits the raw truth to surface.
On Valentine's Day in 1999, Hernan suffered severe head trauma while sledding in the snow-covered mountains above the Los Angeles basin.
Eva says she tried to reach her son but couldn't navigate thick snow and ice. She flagged down a passing vehicle and asked the occupants to alert authorities.
Hernan was airlifted to Huntington Memorial Hospital, where, two days later, he was declared brain dead.
A family care coordinator with One Legacy, an organ and tissue recovery agency, approached Eva and her husband, Arnold, to talk about donating Hernan's organs.
They decided to donate four of Hernan's organs: his heart, liver and both kidneys.
"The right kidney went to an older white gentleman," says Arnold Perez, Hernan's stepfather. "The left kidney went to an older Vietnamese gentleman. His heart went to a young American boy, and his liver was given to a young girl."
That young girl, 9-year old Megan Corfee, recently recalled the day when she and her mother, Debbie, received word that a donor organ was available.
They were at a car wash when the pager from One Legacy started buzzing.
"I called the coordinator and she told me, 'We have a liver for Megan, get here as soon as you can,' " Debbie said. "I was like 'Wow! That was fast, after only being of the donor waiting list two weeks.'"
When Megan was just 7 years old, she was diagnosed with autoimmune hepatitis, a liver disease that she says "made my body think I didn't have a liver."
"I was jaundiced and I was throwing up blood," says Megan, who turns 22 this month. "Basically, when they did the transplant, they said my liver was shrinking, so I was pretty sick."
Four years after her successful transplant, Megan sent a thank-you letter to the Perez family. In the letter, printed on floral paper, Megan tells the unnamed "Donor family" she enjoys music and watching "Cosby Show" reruns.
"I had my liver transplant when I was 9 years old. I am now 13 and I am doing very well," she wrote. "I am very thankful that you decided to have your loved one's organs donated."
Three years after Megan sent that letter, the two families -- who lived about 30 miles away -- agreed to meet.
"Megan Corfee came to gladden our hearts," Arnold Perez said. "To me, she is an angel that was given life by another angel, and in our lives, she is a source of light."
Since they first met in 2006, the Corfee and Perez families get together every year at fundraising events for Donate Life, which handles the national organ and tissue registry and helps to raise awareness about the benefits of organ donations.
The Perezes treat Megan like their own child, and Eva and Megan have formed a particularly close bond, communicating nearly every day, either on the phone or via Facebook.
It's rare for donor and recipient families to meet, let alone forge such a close relationship, according to Bryan Stewart of Donate Life.
"In the case of Hernan, it was devastating for the family to lose him in such an accident," Stewart said. "And yet at that time, they saw the opportunity to leave a legacy of life where they could see Hernan's gift grow into other people."
Megan's mother said that sometimes, the meetings between the two families have "been a little awkward, I think maybe (because of) the language barrier."
But, Debbie Corfee added, "I see, especially in Megan, that it's something that gives her a boost and a spark in life. That life is worth living because of her connection with this family."
On a recent Saturday morning at the Rosemont Pavilion next to the Rose Bowl, the Corfee and Perez families met to help hundreds of other volunteers decorate the Donate Life float for the Tournament of Roses Parade scheduled for January 1.
Eva grasped Megan's hand tightly and said, "Look at the float!"
"One More Day," read the banner, "One more day I can have with Hernan and one more day that people are on the waiting list -- they want one more day to receive the transplant."
Three years ago, the Perez family was chosen to make a floragraph -- a floral portrait of Hernan on the Donate Life float featured in the parade. Eva Perez was selected to walk alongside the float, holding a tether to a hot-air balloon that featured a portrait of Hernan.
"(She) was literally connected to his portrait," Stewart said. "So for her, it was like walking five miles with her son again."
This year, Arnold Perez was chosen by his fellow volunteers to represent them on the Donate Life float. He will be one of 28 float riders.
The Perez family volunteers with Donate Life. Every week, Eva shares her story of loss to visitors to the Mexican Consulate in downtown Los Angeles in the hopes they will sign up to become organ and tissue donors.
Eva Perez credits the organization for giving "my son's death meaning."
"I realize that his organs and his life live on in other people," she said.
With their son never far from their thoughts, the Perez family will spend this Christmas at Holy Cross Cemetery in Culver City decorating Hernan's grave site with tinsel, wreaths and artificial snow as they do every year.
"In the six short years that Hernan was on Earth, it was clear to see that he was a marvelous boy," Arnold Perez said. "The fact that he was so marvelous and generous made it easier for us to make the choice to have him be an organ and tissue donor.
"He was a happy child, and the time that I spent with him and held him were really the joy in my life."