The 12-year-old had his head shaved at an assembly at St Therese's Primary School in Kennington on Monday morning.

Gus' cousins Tahnee and Lukas Cannan both have cystic fibrosis, a genetic life-limiting disorder.

EARLIER: Gus Hay has had fairly long hair for almost his whole life.

But the 12-year-old about to shave off his golden locks for a cause close to his heart - one that affects two of his cousins.

Tahnee Cannan, 27, and her older brother Lukas, 30, both have cystic fibrosis, a genetic life-limiting condition that affects the lungs and digestive system.

"It's heartwarming to know [Gus] is thinking of us, I think it's awesome," Tahnee said.

Gus will shave his hair at an assembly at his school, St Therese's Primary School in Kennington, on Monday morning, with May being cystic fibrosis awareness month.

The grade six student was not nervous about lopping off his locks, saying he just wanted to get it shaved off.

"When I have a shower, I need a lot of conditioner," he said.

He decided he wanted to shave his head for cystic fibrosis last year, and has been growing his hair since November.

Not only is Gus raising money, but his hair will be made into a wig for a child.

Gus said his school had helped his cause, as had his family.

The money Gus raises will go to Cystic Fibrosis Australia, which funds research through the Australian Cystic Fibrosis Research Trust, provides support, and advocates for those with the condition.

Tahnee said she was just three weeks old and Lukas three years old when they were diagnosed with CF.

The condition had had a "massive impact" on their lives, she said, and with medication and treatment a daily necessity, it shaped their day-to-day lives.

But Tahnee said their parents had taught them how to look after themselves, and led them into sport as a way to keep healthy.

This love of sport has seen Tahnee become talented sportsperson and a member of the Lady Braves.

To support Gus' head shave, visit his Everyday Hero fundraising page.

Cystic fibrosis is the most common genetic life-limiting disorder in Australia, with a baby born with the condition every four days.

The condition can occur when two people carrying the CF gene have a child: the child of two CF gene carriers has a one in four chance of having the condition.

People with CF develop an unusual amount of thick mucus within the lungs, airways and digestive system, which impairs digestive functions and traps bacteria in the lungs.

This leads to recurrent infections and subsequently irreversible damage.