And the duo lean on each other when the going is tough or the frustration mounts about the things they can't do, and the limitations that the devices and their conditions place on the active youngsters.

When Jasper was born, pediatricians noticed a heart murmur and further investigation revealed he had the relatively-rare genetic condition hypertrophic cardiomyopathy in which the heart muscle thickens. Testing of the rest of the family revealed Lewis and dad Neil also had the condition.

Jasper, 7, had open-heart surgery on December 19 and spent Christmas in hospital after doctors sought special medical clearance to perform the operation, which is normally done on bigger children.

Testing had shown Jasper's heart muscle had thickened to 19mm when the average adult heart muscle thickness is about 11mm. Doctors decided it was too dangerous to delay the operation and the family had less than 24 hours notice that the surgery was to take place.

It was dejavu for parents Stephanie and Neil, who had sent Lewis off for the same surgery less than 10 months earlier in March.

Lewis suffered a cardiac arrest during a family trip to the beach at Altona and his parents revived him with a portable defibrillator that had been told to always carry. After being rushed to hospital Lewis had his pacemaker and implantable defibrillator placed in his chest.

"Jasper's only just had surgery and you can't stop him, but that's his nature though ... he's full on," Ms Wilson said. "Whereas Lewis took two and a half terms to get back to school full time, but he had had the cardiac arrest."

"Because Lewis had a cardiac arrest that increased Jasper's risk, but his heart thickness had also increased at our last visit so they decided to put it to the (Royal Children's Hospital medical) board to get approval.

"Jasper's heart thickness was 19mm, which was worse than what Lewis was at that age."

If not for Jasper's diagnosis at birth, the family would never have known Lewis also had the condition and he likely would have died when he suffered his cardiac arrest.

"I actually cried in the pediatrician's office saying thanks for picking it up in Jasper seven years ago, or Lewis wouldn't be alive," she said.

Like Lewis, physical restrictions had just been imposed on Jasper before his surgery. The restrictions meant the boys could not play sport and do anything strenuous or vigorous - a tough things for two sporty and active boys.

"It broke Lewis' heart because he loves his sport - he would do anything to play football or basketball. To him that was a really hard one but since his cardiac arrest he's had a lot of fear and is very, very cautious," Ms Wilson said.

"Jasper, it's hard to explain to a seven-year-old boy. He's on the spectrum so we do visual cards which helps him at school, as does having Lewis there."

The cardiac pacemaker and implantable defibrillators impose their own limitations, including how close the boys can hold mobile phones and other electronic devices, and there's no monkeying about on monkey bars or hanging by their hands.

"Jasper will often ask Lewis what did you do with this or how did you do that, and because they can't have a phone too close to the defibrillator because it can set it off, he'll ask Lewis 'is this the right amount?' and Lewis will sometimes try to slow Jasper down," she said.

The family make the trip down to the Royal Children's Hospital every three months to get their pacemakers checked, and twice a year they have full cardiac testing.

Since their surgery, neither of the boys' defibrillators have been needed to restart their hearts but Lewis' pacemaker kicks in sometimes at night when his heart rate drops.

"Because of the fear of the unknown and trauma, we were hung up on that for a long time with Lewis but now we are getting around trusting that (the devices) will work when they need to," Ms Wilson said.

But the surgery and devices are not a cure. There is little research in to HCM and every child with the disease is different. The boys will need further surgery as they grow to ensure the leads remain connected between the heart and the devices, and to replace the batteries.

READ MORE ABOUT LEWIS AND JASPER'S STORY

Throughout the family's horror 2019 they have found strong support from family, friends, their community and the charity HeartKids.

Lewis' life was saved with one of two defibrillators purchased for the family after a friend started a Go Fund Me campaign, and the Wilsons are returning the favour, raising funds to buy defibrillators through Defibrillators for Life for other families whose children are at risk of cardiac arrest.

"The more families that have access to defibrillators, the more children whose lives can potentially be saved," she said.

February is Heart Kids month raising awareness and funds for children with congenital heart disease.

"When we went in for Jasper's surgery, I was not prepared. HeartKids had a bag of gifts for all the children as I had left the Christmas shopping until the last minute," Ms Wilson said.

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