'Real-life Fault In Our Stars' couple Katie and Dalton Prager have said their final goodbye over FaceTime.

After five years of marriage, Katie and Dalton Prager, who have been dubbed the real-life “The Fault In Our Stars” couple, said their final goodbyes over FaceTime on Saturday after a failed reunion.

“She told him that she loved him,” Katie’s mother told Fox 5. “We don’t know if he heard her.”

Dalton, 25, died in St Louis from complications related to cystic fibrosis, which both he and his wife had.

Katie visiting Dalton in hospital. Source: Facebook

He had been trying to get to Kentucky to see the 26-year-old who is currently in hospice care in her home there.

"My angel, my best friend, the love of my life, my husband went to be with the Lord our God today," Katie wrote on the pair's joint Facebook page on Sunday night.

"Dalton fought a long hard battle with Cystic Fibrosis. He was a courageous fighter and 'give up' wasn't in his vocabulary."

The last time the couple saw each other was their fifth wedding anniversary in July this year.

Cystic Fibrosis is a chronic, life-shortening illness that affects the lungs and digestive system.

Katie and Dalton met online when they were 18-year-old and were warned against meeting face-to-face because Katie risked contracting Burkholderia cepacia, a highly infectious bacterial infection which Dalton had.

She ignored the warnings and invited him to visit her in Kentucky, they fell in love and were married two years later, not unlike the two teenage cancer sufferers in John Green's novel The Fault In Our Stars.

The couple early on in their relationship. Source: Facebook

"I told Dalton I’d rather be happy — like really, really happy — for five years of my life and die sooner than be mediocre happy and live for 20 years," Katie told Fox 5.

"That was definitely something I had to think about, but when you have those feelings, you just know."

She did, eventually, catch the infection.

Both Katie and Dalton underwent lung transplants, in July 2015 and November 2014, respectively.

Both Katie and Dalton suffered complications after their lung transplants. Source: Facebook

Unfortunately both suffered complications afterwards.

Dalton battled with cancer, pneumonia and a virus and spent the final months of his life on a ventilator, while Katie's new lungs simply didn't take and she was repeatedly in and out of hospital.

She currently survives on an oxygen tank and on Saturday afternoon, just hours after she became a widow her family celebrated an early Christmas for fear she won't make it until December.

Even so, she says she has no regrets about meeting her husband.

"He meant everything to me," she told the Lexington Herald Leader. "I’ll see him soon."

Feature image: Facebook