Todd Sampson grew up thinking his sister was his cousin. He found out the truth by secretly recording his parents.

When Todd Sampson was a child, he received a tape recorder as a Christmas present. 

As an investigative little kid, he would put the recorder under the family sofa when he went to bed and record his parents' conversations. 

The next day with his mate Herbie, he'd listen back. 

One day, he overheard his parents in the recording debating whether or not to tell him that his cousin Wendy, was actually his older sister.

Todd Sampson as a boy (left) and his parents (right). Image: ABC.

"They were debating whether we were old enough to comprehend what had happened and to accept it. So I went to mum and said: 'Is Wendy my sister?' I remember her face - it was shock and relief. She said yes. And then, it was only as an adult many years later I reconnected with Wendy as my older sister. Now I am super proud she is my sister," Sampson told Anh Do's Brush With Fame. 

His mother had Wendy at the age of 15, alone in a room, in a very strictly religious community. She was told she had to give her up for adoption, so she handed over her newborn to her sister.

Sampson, who you'll most likely recognise from the ABC comedy series The Gruen Transfer, or the documentary series' Life On The Line, has spoken about uncovering his family's secret while reliving his upbringing in a poor government housing dominated area of Sydney, Nova Scotia, Canada. 

A crying mess I’m guessing. https://t.co/Yu88fR7bU3

— todd sampson (@toddsampsonOz) September 22, 2020

Sampson's father was a labourer and spent his entire work day pouring sugar into vats at Coca Cola. His mother worked at KFC on the checkout.

He remembers trying to stay awake for her to return from her midnight finishes, only to be woken up by the smell of KFC as she walked through the door.

"What I remember most about that place is feeling this sense of community. Everyone's struggling there and I remember growing up with kids and having so much fun - not having a lot - but not noticing it. But my parents were very stressed about putting food on the table," he told Do.

Sampson grew up in an impoverished small town in Canada. Image: ABC.

"I remember my dad got sick, and he wouldn't stop working, and he was blacking out, but he didn't stop working because he needed to provide," he said.

Thinking back, it was a comment from his father that would go on to sculpt his life's purpose.

"One day when I was a kid I was joking about his [my dad's] hands being hard. They were all calloused, and he put his hand out and put my little hand over his and said 'son, you do not need to have hands like this, you can use your mind, and you can do better things than I have done'. It's a moment I will never forget," said Sampson. 

"If my life is defined by fear and curiosity, it's also defined by the fear of being poor," he said.

To begin with, Sampson would spend his school days mucking around with his mates in classrooms.

But then his science teacher saw potential in him and got him put into the 'special' class at school, usually reserved for the kids of the more wealthy families in the area.

"I thought they'd made a mistake, and I didn't want to be in that class... none of my friends were there," Sampson remembered.

He went home and told his mum who said "okay, I'll sort it out," and went down to the school.

WATCH: Sampson telling Anh Do about being put in the 'special class.'

"They said 'this kid's got ability and we want to try him in this class'. I remember two days of not talking to my mother for giving in to the school," said Sampson. "But something changed. A combination of insecurity and competitiveness, and I thought to myself these kids are not better than me because my mum works at KFC and my dad works at Coke and their parents are doctors and lawyers. I am going to study and that was it. I went from bottom of the class to the top of the class."

Ahead of his last two years of highschool, a 16-year-old Sampson won a $30,000 scholarship to Pearson college, which took on 200 students from more than 100 countries, with the goal of making education a force to unite people, nations and cultures for peace and a sustainable future.

Suddenly Sampson was sharing a room with four other people from four different continents and he says it was the moment that "just smashed open my world."

At the age of 16, Sampson won a scholarship to a college attended by students around the world. Image: ABC.

After attending business college he fell in love with marketing. Sampson rose up the ranks of the advertising world, eventually becoming CEO of Leo Burnett Australia where he co-created Earth Hour, one of the largest environmental movements in history, reaching more than 1.4 billion people in more than 5,500 cities.

The now 50-year-old has not only carved out a successful business and advertising career but is also an award-winning documentary maker and TV presenter, who lives in Sydney, Australia, with his wife Neomie and two daughters, Coco and Jet. 

TODAY is LAUNCH DAY and it started with my Neomie giving me a bit of perspective: “Just remember childbirth is harder and infinitely more dangerous than anything you’ve done! it’s the real #BodyHack” @bodyhackau @Channel10AU pic.twitter.com/siRCrcdWcx

— todd sampson (@toddsampsonOz) June 24, 2019

But of all of his successes, he says a phone call he made to his dad is his proudest moment.

"I phoned him and I said to him, 'dad you will never have to think about money again,' and he just cried," he told Anh Do. 

Sampson's parents. Image: ABC.

"That was one of the proudest days of my life.... They deserve it. Anything and everything I've done is because of them."

Feature image: ABC.