Brady Riley, Lucas Evans, Ashleigh Mabbett and Zach Walker, all of Dunedin, share a special connection - they all have hypoplastic left heart, a condition where the heart's left side is underdeveloped.
Their mothers also have a special understanding of each other's challenges and when they met 12 months ago, open heart surgery and intensive care were very recent memories.
A year on, the mothers and their children have met again, with the help of support organisation Heart Children New Zealand, sharing stories of their children's progress.
Heart Children New Zealand's annual appeal week, Heart Kids Week, runs until Saturday.
Debbie Riley said despite Brady's rocky start, he was now just a normal 19-month-old and no longer required medication.
"Everything is as it is meant to be. It's a lot of stress off me now. It's really good not to worry."
While there was the prospect of a future operation to replace a heart valve, life had returned to normal for Brady and the family, she said.
Having reached the 2-year milestone, Lucas recently underwent more tests in Auckland - the results of which were good, his mother Anglea Evans said.
Lucas was also part of a brain study looking at the effects lack of oxygen can have on children's learning.
He also passed those tests with "flying colours".
"They were pleased with him. He's just a normal boy."
Ashleigh's mother Theresa Wallis said the situation was very hard in the beginning, and while she also faced another surgery before she was 5, Ashleigh was a "very happy, content wee girl".
There had been a few hiccups for Zach - he had been admitted to hospital twice with infections - but his mother Sarah Walker said nothing could slow him down.
"I expected him to be more sedate but he runs around, then lies down and has a little rest, and then goes again."
While doctors had ruled out the likelihood of serious complications, he would need more surgery in time.
"I hope after that things normalise. I don't want the heart condition to rule his life. I don't want him to be 'that heart kid', I want him to be Zach."
Childhood heart disease
> Heart disease is leading cause of death in young children.
> Every week 12 babies are born in New Zealand with a heart defect.
> More than half of the defects require treatment through medication or surgery.
> Up to 20% of defects are gene-linked.
> In about 80% of cases cause is unknown.
> Nearly twice as many children die of congenital heart disease than from childhood cancers.
> Every year 450 children will have open-heart surgery.
> 70% of all heart surgery involves stopping a child's heart.
> 1000 children a year are treated at Auckland's paediatric cardiac unit.
Source: Heart Children New Zealand
