Dalton Prager met his wife Katie online when they were just 18 years old.
The pair began speaking after Katie saw a photo of Dalton on Facebook, realising he also suffered from the genetic chronic illness Cystic Fibrosis she reached out to him.
'Hey, I see you're in the hospital if you ever need somebody to talk to,' Katie wrote to him. 'I'm sorry, but do I know you?' Dalton responded.
They continued an online friendship, but doctors urged them not to meet up in person as Dalton had Burkholderia cepacia, a highly contagious infection for people with cystic fibrosis, and Katie didn't.
'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 said. 'That was definitely something I had to think about, but when you have those feelings, you just know.'
They married in 2011 at the age of 20.
Katie and Dalton went through their battles together. In August 2014, Dalton was told he wouldn't live to see Christmas if he didn't receive new lungs.
In November Dalton received his new lungs, and the pair were kept apart until Katie received hers eight months later. Only after Dalton's transplant would Katie's mother learn, she had taken her own name off the transplant list to ensure Dalton got his lungs first.
As their story garnered international attention, they were often referred to as the “real life” Fault In Our Stars couple. But much like the film’s main characters, their story would not end as you might hope.
Soon after Katie’s transplant, her lungs began to fail. Dalton developed lymphoma and eventually so did she.
After overcoming his cancer, Dalton contracted pneumonia and was attached to a ventilator at Barnes-Jewish Hospital in St. Louis. He spent the last two weeks there, while Katie entered end-stage renal failure. Earlier this month doctor’s told her there was nothing more they can do.
Due to their illnesses the couple were not able to be reunited, and the last time Katie and Dalton saw each other was on their fifth wedding anniversary on July 16.
The couple were left with only the option to FaceTime as Dalton lay dying this weekend, and the last thing Katie said to her husband was that she loved him.
"She told him that she loved him," Katie's mother said. "We don't know if he heard her."
The day before her husband passed away, Katie told CNN:
"It gave me some of the best years of my life. I’d rather have five years of being in love and just really completely happy than 20 years of not having anybody."
"We told each other we loved each other the first day we met in person. We just knew," Katie said. "He understood everything about me. He knew what I was going through, and he was just my other half. And I knew it."
"He was one of the greatest people I'd ever met and not many people like Dalton come around so you got to get him while you can," she continued.
Katie wrote on Facebook on Sunday, with an announcement about her young husband's death:
"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."
Katie spent the last few months of her life in hospice care, passing away only days after her husband. Her mother announced her passing on Facebook:
“Early this morning, she gained her wish of being at home, in her bed, surrounded by her mum, dad, brother and her dogs, dying peacefully, away from the hospital, tubes, IVs,” Ms Donovan, wrote on Facebook.
“The days to follow will not be easy but I find comfort in knowing that my girl lived, she really lived.”
Updated 23rd Sept, 2016.