In an interview during the show's finale, Luke became emotional as he and his brother shared how their father, who suffers from mesothelioma, a rare cancer that arises after exposure to asbestos, was their motivation for getting through the show's challenges.
Josh teared up, when speaking about the life expectancy following a diagnosis, saying it's between two and five years generally.
"One of our motivating factors and something that got us through is obviously with our dad. He hasn't been well recently. The average life expectancy when you've been diagnosed with mesothelioma is about two years to max five," Luke said.
Josh broke down in tears, saying their father's diagnosis was "hard to process".
"It's hard to talk about sometimes. We don't really bring it up. We try to stay as positive as we can about it, but you don't like thinking about these situations... the way it can go. It is hard to process," he shared.
Mesothelioma can take between 20 and 60 years to develop and affects the lungs, but can also affect the stomach, heart and other organs, according to the Cancer Council.
Viewers were left heartbroken by the moment, taking to Twitter to share their thoughts.
"Regardless of everything else, I do feel for the twins. They love their dad," one user wrote.
"Every time Josh and Luke talk about their dad. Truly can't handle," another said.
"I'm so happy for Josh and Luke!! Made their sick dad proud as punch. Well done boys!" a third added.
The boys have previously spoken about wanting to make their time on the show "worth it" as they're "losing that bit of time" with their dad.
Josh shared in a piece to camera that he and Luke "always look to impress" their parents.
"This is the biggest thing we've ever done in our lives and we'd love nothing more for them to really enjoy every room and space we've been building together. So that would be massive for us to gain their approval and for them to be proud," he said.
He added that their parents are "very honest" and if they found a fault in their design or styling, they'd "have to think about having major change".
Josh and Luke no doubt made their family proud after placing second on auction day.
The twins' had a new reserve of $3.4 million, down from $3.5 million, and sold their property for $3,930,000, with a $530,000 profit.
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