In the end, the love story between Dalton and Katie Prager ended as it had began.
The pair met online before marrying in 2011, and just before Dalton died on Saturday afternoon, he FaceTimed his wife to say one final goodbye.
The young couple's relationship had become known as a real life version of that at the centre of the movie and book
The Fault In Our Stars. Dalton, who was 25, had long battled with Cystic Fibrosis (CF), and over the past two weeks had been on a ventilator in intensive care due to complications caused by a new infection.
Katie, who also has CF, was in a hospice in Kentucky, and so was unable to be by her husband's side in St Louis, Missouri, in his last moments due to the highly contagious nature of his illness. Both of them were too ill to travel to be by one another's side.
So Katie said goodbye to Dalton on FaceTime instead. Her mother, Debra,
told CNN: "She told him that she loved him. We don't know if he heard her."
According to CNN, the last time the couple saw saw each other was on July 16 to mark their fifth wedding anniversary.
The two met on Facebook when they were teenagers, and ignored the advice of doctors by meeting in person and becoming couple.
"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. That was definitely something I had to think about, but when you have those feelings, you just know."
Both of them qualified for and received transplants between 2014-15, but neither one's health ever improved.
After Dalton passed away at the weekend, Katie and Dalton's mother paid tribute to him on the couple's Facebook page.
Katie wrote:
"My angel, my best friend, the love of my life, my husband went to be with the Lord our God today. Dalton fought a long hard battle with Cystic Fibrosis. He was a courageous fighter and 'give up' wasn't in his vocabulary. Thank you for all of your love, prayers and kind words that you have shown to us over the past few years. God bless each of you. - Katie"
Meanwhile, Dalton's mother said:
"Today.....September 17, 2016 at 12:56 Dalton Lee Prager joined his sister, Samantha, and grandfather, Larry, in Heaven. You may Breathe Easy now my son. You are my true hero. ~~Love Forever, Mom"
An online fundraising page has been set up to cover the costs of Dalton's funeral, which will take place on Wednesday. It's not known yet whether Katie will be well enough to travel to it.
