Since those early performances, the creative pair have followed similar paths - both attending Toi Whakaari: New Zealand Drama School. But despite moving in similar circles, Liv says there has never been any tension or rivalry about following him down the same career path.
"He's always just encouraged me, it's been amazing," she says. "We kind of joke about that, but there's never any resentment."
Instead, working together on Sibs has been a relative breeze, the ease of their 22-year relationship making for quick and easy shorthand.
"You don't have to go through that awkward patch of being unsure how to reject their ideas," Liv says. "We can just say 'no, that's shit', and move on."
With old home-video footage woven into the show, Sibs will take the audience back to their Christchurch family home in the late 90s, while exploring the unique relationship between brothers and sisters.
"I think the home footage acts as the trigger point for stuff to emerge out of that's the root of where we started. And then around that we've made a series of sketches and stories and played around with the dynamic of having a sibling," says Chris.
"We can go way further with each other than a normal duo could," Liv adds. "There's a thing about siblings where you can be so awful to each other but at the end of the day you still love each other."
She says the show will touch on forgotten memories and experiences, including how siblings can remember the same events differently.
Part of that comes from Chris' experience of growing up gay but feeling unable to talk about it. Having a much younger sister gave him a new avenue to express himself, particularly through playing with her dolls.
"You can hear this inner turmoil of 'I shouldn't be doing this but it feels so good'," he says.
"I said to Liv 'didn't you feel betrayed that I didn't want to play with you anymore', and Liv's like 'I didn't really think of it that way'."
Yet while Chris has made a name for himself exploring his sexuality on stage, including in his Fred Award-winning Camp Binch at this year's Comedy Festival, he says he wants this piece to be different.
"I come from a long lineage of really queer comedy now. I'm really enjoying making it about something else, that sibling dynamic. It's undoubtedly coming into the conversation, but it's really fun to play around with this relationship."
While devising and staging a show is a daunting task for anyone, the pair will also have to contend with their family coming up and witnessing the siblings take on the past.
Although, given where the show came from, it's unlikely anyone will be surprised.
"It'll be authentic to what we were doing our whole lives," Chris explains. "So it's literally what we were doing at home, but on stage as adults."
LOWDOWN:
Who: Chris and Liv Parker
What: Sibs
Where: Basement Theatre
When: August 7 to 11
