Thanks to that business relationship, the Methven family rose to become the third-richest family in South Africa.
Mr Methven was killed in a motorcycle accident in 1986 and the family sold the company in 1991 — the year Ms Methven was born. They no longer have any ties with the food chain.
While it is not known to what extent that sale lined the family's coffers, Ms Methven spent her childhood in the lap of luxury.
Her mother Lisa moved to the United States, where Kaila was born, and she grew up in a mansion in swanky Beverly Hills.
FAMILY TRAGEDY
But despite that wealth, the Methvens were not immune to tragedy. When Ms Methven was just a few months old, her Tunisian Muslim father left his partner and child.
Her mother battled alcoholism and was eventually diagnosed with cirrhosis of the liver, which caused her health to deteriorate.
At the age of just 14, Ms Methven's mother died by suicide and her mum's boyfriend — the only father figure the teen ever knew — decided he couldn't raise her alone.
The girl had a grim choice: go into foster care, or move to Paris to live with her estranged father.
TROUBLED TEEN YEARS
The move to France was a shock for the young girl, who had spent her life in a Los Angeles luxury property. Suddenly, she was plunged into financial hardship, sharing a tiny apartment with a father she never knew, her difficult stepmother and the couple's four children.
The French-speaking, strict Muslim household was also a difficult environment for Ms Methven, who had been raised by her agnostic mother.
In an interview with Medium late last year, Ms Methven revealed new details about that troubled time, which she described as "abusive".
"Boy was I in for the ride of my life that completely changed me and my every perspective on life," she told the publication. "While living in France, I grew up in a strict Muslim household were French was spoken (I didn't speak French).
"We were seven people living in a one-bedroom apartment on the outskirts of Paris, a two-hour train ride from the city centre. I slept on the kitchen floor for about three years and worked as many jobs as I possibly could.
"This Beverly Hills girl had gone from a mansion on Rodeo Drive to the ghetto suburbs of France, literally in an area that would appear on BBC news due to the constant bombing and vehicles lit on fire."
She said the situation was "overwhelming" to experience at such a young age.
"I couldn't talk to anyone, I was broken, and had just lost my mother," she told Medium. "On top of it all, I had four brothers and sisters and a stepmother with whom I did not get along.
"This whole situation was a pretty mentally abusive experience for me, but I believed there were better things for me out there."
A BRIGHTER FUTURE
Ms Methven was determined to succeed, graduating top of her class and eventually studying fashion and moving back to the US in 2014.
Since then, she has founded two high-end lingerie brands, Madame Methven and Latrodectus, and amassed millions of followers on social media.
Ms Methven, who describes herself as a "KFC heiress" on her website, has had her designs worn by scores of celebrities including singer Demi Lovato, the Kardashians and actor Katharine McPhee and they have been featured in a range of publications including Harper's Bazaar, Elle and Love.
It is not known how much of the family fortune she inherited after her mother's death, but in a 2018 interview with Business Insider, the CEO said her own brands were expected to rake in up to US$10 million ($15m) over five years.
She told the publication her inherited wealth could be a burden at times. "As an 'heiress' I feel like any other person, just with more financial responsibilities and more stress," she said.
"As with most people, the more money you have, the more problems you attain."
