From PEOPLE Magazine Click to enlarge
Huddled around the kitchen table with a stack of papers and markers, 7-year-old Avery Toole and 8-year-old triplets Austin, Miles and Tai Lawyer comment on their artwork. "I love mermaids," declares Avery, brushing long curls from her face and hunching over the bright blue tail fin she's sketched. "I'm making a whale," says Austin. Missing from the scene is the boys' big brother Dalton, who was killed in an accident, but he is the reason Avery is here. "I have," Avery explains, "Dalton's heart inside me."

Worlds collided in early August 2009 as two desperate couples 700 miles apart each prayed for a miracle. In Boston, Mike and Cheryl Toole stood at the hospital bedside of their only child, Avery, who needed a new heart to survive. In Toledo, Ohio, Jim and Jeri Lawyer wept, watching over the oldest of their four boys, Dalton, 8, who was hit by a truck while riding his bike. The Tooles' prayers were answered at the same time doctors declared Dalton brain-dead and the Lawyers agreed to donate his organs. What no one could anticipate: The Lawyers' amazing act of generosity would not only give Avery a second chance at life, it would also unite two families in a way that gave solace to grieving parents. Says Jim Lawyer, 52, an anesthesiologist: "I think Dalton's heart was destined for Avery." Cheryl Toole also feels fate was at work: "Dalton saved Avery. And we've been given a new family."

For Mike and Cheryl Toole, the unmitigated joy of their baby girl's birth lasted less than 24 hours. At 1 day old, Avery was diagnosed with hypoplastic left heart syndrome-a rare heart defect. Mike, 43, a TV news producer, and Cheryl, 44, a neonatal nurse at Children's Hospital Boston, tried to give Avery a normal childhood. But by the time she'd reached kindergarten, she'd been through eight open-heart surgeries. "She was slowly dying," says Cheryl. "We talked to her about heaven. We tried to prepare her."

Unlike Avery, Dalton Lawyer led a charmed life. A swimmer who loved superheroes and roller coasters, he got the nickname "Diesel" for his initials, DCL, and his turbo-charged approach to life. He displayed his trademark brio that July 30 afternoon, rushing out of his aunt's house to catch up with cousins at a nearby park. "I love you, Mom!" he called out. Minutes later a truck hit him head-on. His frantic mother rushed to his crumpled body and began CPR. But Jeri, a former nurse, knew his condition was dire. "We were devastated, we were basket cases," says Jim.

On Aug. 6 the Tooles got the call: "A perfect heart," they were told, was on the way. Searching the Internet, Cheryl found Dalton's story in the news. "I told Mike," Cheryl says, "'That's him. I just know.'" During a complex 18-hour transplant surgery, Dalton's heart began beating in Avery's chest. "She was the highest risk of any patient we had seen to that point," says her surgeon Dr. Francis Fynn-Thompson.

Ignoring advice to wait at least a year before reaching out to a donor family, Cheryl sent a heartfelt letter of thanks just three months later. It was delivered to the Lawyers, who were struggling with their loss. "I begged God," says Jim, "to let me dream about him." Yearning for a connection with his son, he immediately responded to the Tooles. "I miss my boy terribly," Jim wrote, sharing stories about "the boy who answered your prayers." The families agreed to meet on Martha's Vineyard on the one-year anniversary of Dalton's death and Avery's transplant. "Friends thought we were crazy," Jeri, 50, says.

The families bonded instantly. Avery, though on medication and banned from some contact sports, was healthy and full of energy and mischief. And she was delighted to meet these new sort-of siblings, boys she now calls "my brothers." The triplets told her stories of Dalton, and she let them place their heads against her chest and listen to their brother's heart. "I loved my brother," Austin says, "and now I love Avery. She is one awesome sister."

These days the families see each other several times a year. The kids build forts and play hide-and-seek and the grownups linger over the dinner table; sometimes there are tears. But there is also talk of cooking and football, of children's books and bedtime schedules, as life for these now forever-linked families goes on. And, perhaps in the ultimate tribute to the boy that saved her life, Avery isn't wasting a minute. "I love crafts, I love unicorns, I love every single food," she says. "I love everything in this whole wide world."