Parents hear their daughter's heart beat again after her death.

And once again, I’m crying at my desk.

A North Carolina boy got a new life when, after 99 days in the ICU, he received a heart transplant. Four months later, he met the family of the girl whose heart beats in his chest.

In March this year, 14-year-old Katelyn Zimmerman and her 13-year-old brother Dylan died after they were hit by a car while riding their bikes near their home in Florida.

Earlier the same day, Katelyn had told her grandmother Carlene Sweigart she wanted to be an organ donor.

“I told her that I was proud of her and I’m an organ donor and her great grandfather was,” Sweigart tells ABC News. “Three hours later, she was gone.”

After the accident, Sweigart told Katelyn’s father, Shawn Zimmerman, about her wish. The family decided to donate her organs.

On the other side of the story is 14-year-old Albert “Alj” Jeffries, who was born with dilated cardiomyopathy, a chronic heart disease that leads to an enlarged heart and eventually to heart failure. The disease, which took the life of his sister at age 19, meant Alj couldn’t run around like normal kids. He spent his entire childhood in and out of the University of North Carolina Children’s Hospital.

When he was 12, Alj’s heart failed. Though doctors were able to temporarily fix the problem, the issue came back in 2015 and he was added to the heart transplant list.

“We were really starting to lose hope,” Tina Turner, Alj’s mother, tells Today.

After 99 days in the ICU, Alj’s family found out there was a heart available that matched him.

“It is amazing! I thought I was going to lose my son,” Turner says.

Soon after this, Sweigart saw Alj's story on the news. She started to follow his Facebook page, Team Alj, and eventually reached out.

As Today explains, "donor families are not encouraged to contact recipients and their families," but Turner wrote back.

"Zimmerman is going through so much," she says, "and still made it [life] possible for so many people."

On Monday July 25th, the two families met for the first time. They recorded the emotional meeting on Facebook Live, where Katelyn's family were able to listen to Katelyn's heart beat inside Alj's chest.

"She was there," says Sweigart. "I can feel the love of Katelyn."

The video also shows Alj sharing a letter with Katelyn's family.

"Thank you for a second chance at life. There were times when I couldn't breathe, and couldn't walk without breath. I needed a miracle," he reads. "Katelyn, thank you for being my miracle."

"I'm ready to get out there and spread the awareness of organ donation," Turner tells ABC News. "This is what life is all about. With life comes death and with death comes life. After Katelyn made that wish, her family didn't think twice about it. They saved our family from a lot of heartache."

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