The Block contestants dubbed "the stylish grandads" – have been in a solid relationship for 14 years. But their happiness has been a long time coming.
Mitch didn't come out as gay until his mid-thirties, by which point he'd married and had three children. He says being gay "wasn't an option" for him growing up.
"I thought being gay was wrong," Mitch, 56, tells TV WEEK.
Mitch went on to get married at age 22.
"I felt terrible, because we were playing happy families," Mitch recalls.
"I was doing well at work and thought, 'If I do more and earn more money, I'll eventually feel better.'
"But my wife knew something was wrong and it [him being gay] finally came out. We tried to make things work, but it was never going to, so we ended up going our own ways. It was traumatic."
While coming out spelled the end of his marriage, Mitch says it was "the most amazing relief".
"I thought, 'Oh, my God – this is what happy is.' It was probably the first time I really liked being me."
And Mitch's family has accepted him for who he is.
"He's an amazing, loving father and thinks the world of Mark," Mitch reveals of his dad.
Meanwhile, Mark came out at 21 – he knew he was gay when he was about nine – and faced his own challenges.
"In that era [the early 1980s], everything you saw was about HIV," he explains. "My mum found it difficult. I remember her telling me she'd gone to a doctor because she felt so anxious about it all.
"She was given medication to deal with her anxiety, but after a few weeks, she said she'd thrown it out because me being happy was the most important thing."
Despite the same-sex marriage law being passed in Australia in 2017, the pair aren't overly fussed about making their relationship "official".
"We've been together 14 years, so we're basically married in terms of who we are!" Mark, 57, says. "But it [same-sex marriage] is really important to us. I never thought I'd see it in my lifetime.
I had grown up feeling I was on the outer. It was the first time I felt like my country said I was OK."
However, they have discussed having kids of their own.
"I did think it would be nice to have that mid-life crisis that second-marriage guys tend to have," Mitch says with a laugh. "But if we had that [children] instead of going to Europe for four weeks every year, or ducking over to the tropics, the thought passes immediately!"
The Block airs Monday to Wednesday, 7.30pm, and Sunday, 7pm on the Nine Network