On one incredible day in 2011, Brett and Tony's two Indian surrogates each gave birth to twins.
The couple from Bendigo in Victoria went from having no kids to having four baby boys: Ajay, Gyan, Taz and Jagan.
"We didn't know any different, so we just rolled with it," Tony, 49, tells TV WEEK.
He's among the parents in new reality show Parental Guidance, hosted by Today's Allison Langdon alongside parenting expert Dr Justin Coulson.
The new parents were given Tizzie Hall's book Save Our Sleep, which outlines strict routines for babies.
Tony says that although he and Brett followed them to the letter, there were many times they called Tizzie some "nasty names", such as when the routine called for them to take the babies for a walk at 7pm.
"I was walking up a hill one night going, 'I've never been so tired in my life – I could sleep on this asphalt.'"
But he says it worked for them.
"The boys slept straight through from 13 weeks old," he says. "I think having such a methodical, structured approach to parenting saved our lives."
Brett, a teacher, and Tony, a social worker, have some emotional moments on Parental Guidance. In the "stranger danger" challenge, an actor approaches the boys, now nine, at a playground to try to convince them to go with him "to see his puppies".
"That challenge was confronting to watch," Brett, 50, says, admitting it made him cry. "It was hard to watch the other families' kids walking off with the stranger," he says. "It hit home."
Liadhan, Richard and their five kids have spent 64 of the past 65 nights sleeping in their swags under the stars. The other night was spent in a tent because it was raining.
"There's a rhythm to it," Richard, 67, says of the South Australian couple's nature-based approach to parenting. "We spend most of the days with our children as a family unit."
"And there's beauty and stuff to discover," Liadhan, 45, adds.
Liadhan already had two children when she met Richard, while he had four. Together they have Miriam, 12, Hannah, 11, Esther, nine, Eva, seven, and five-year-old Danny.
Richard, a retired teacher, and Liadhan are believers in "unschooling" – or, as Liadhan prefers to describe it, "natural learning, as if school doesn't exist".
"We're involved," he says. "But it's when they're ready and it's led by them."
This approach causes controversy when the other parents learn that the couple's three youngest children aren't reading yet.
"They're in the process of learning," Liadhan says. "The older ones are both avid readers. They went from Dr Seuss to Harry Potter within a year because that readiness and enthusiasm were there."
The couple say they both used to be strict, and would even smack their kids. The discipline discussion on the show brings up "powerful emotions" for them.
"Midway through our parenting we changed our style when we saw some of the issues and damage that had happened for our older children," Liadhan explains.
If there's one question guaranteed to spark a debate, it's the age-old "Should you smack your kids?"
Smacking is among the methods strict parents Andrew and Miriam use when their children, Luke, 12, Grace, 10, and Tim, five, get out of line.
This week, the couple found themselves under fire when the other parents didn't agree with their choice of discipline.
"We knew this would be a controversial topic and it was challenging to be so vulnerable about our parenting on national television," Miriam, 41, admits to TV WEEK
"We're not big advocates of smacking, but we've found this correction tool helpful in a certain circumstance in the younger years."
After taking on board the feedback from the other parents, the couple spoke to their own parents, their siblings and their kids about how they felt about smacking.
"These conversations were enlightening," Andrew, 39, says. "It was good to hear that our older children didn't feel that being occasionally smacked as a child had negatively impacted them, but helped them grow."
PARENTAL GUIDANCE SERIES PREMIERE Monday to Wednesday, 7.30pm, Nine Network.