Dalton Prager breathed his last at a St. Louis hospital on Sept. 17.

A real-life The Fault in Our Stars couple with Katie Donovan, Dalton had cystic fibrosis. Katie had the condition as well, and that's what made it difficult for the two to be together. However, against all odds and the advice of their doctors (it's a bad idea for cystic fibrosis patients to meet because they might make each other sick with infections), the two became a couple, even getting married in 2011.

In fact, the last time they saw each other was on their fifth wedding anniversary last July 16.

The couple both received lung transplants in an effort to get well from cystic fibrosis, but the procedures didn't result in desired outcomes.

Dalton received his new set of lungs first and was doing fine for a while until he was diagnosed with lymphoma. He beat the cancer but later on contracted pneumonia and a viral infection.

Katie, on the other hand, was in and out of the hospital after her transplant until the doctors finally told her that they've done everything they could for her, putting her in hospice care.

The plan was for Dalton to fly to Kentucky where Katie is. Unfortunately, he never got well enough to travel. Too weak to fly, he missed his wife's final kiss.

Katie took to Facebook to post about her husband's passing, saying that Dalton was a fighter and "give up" had no place in his vocabulary.

"Dalton fought a long hard battle with cystic fibrosis .. Thank you for all of your love, prayers and kind words that you have shown to us over the past few years," she wrote.

"You may breathe easy now my son. You are my true hero," Dalton's mom said, in the same post.

Where It All Began

Dalton and Katie met when they were 18 years old. They met on Facebook, with Katie making the first move by sending Dalton a message telling him that she understood what he was going through and that's she's there for him.

Eventually, their friendship blossomed into romance. With the two in love, they were eager to meet each other, but Dalton had his reservations because he had Burkholderia cepacia, a highly contagious disease found in people with cystic fibrosis.

Not that Katie minded.

"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," she said.