They were born in Melbourne after Jonathan and his former partner Selina Korenhof moved to Australia in 2012.
She and his family are trying to bring his body home for burial - but flying everyone back to New Zealand so close to Christmas was too big a cost to shoulder alone.
"It's so expensive - more than what I assumed," Korenhof told the Herald.
"I loved him like he was my own son," he wrote in an emotional plea for help bringing Jonathan home.
Korenhof (seen here with son Asher when he was a baby) was fit and active, but could be lax about managing his diabetes, his former partner said. Photo / Supplied
A flight has been booked to bring his body back, and his family hoped to join but weren't yet able to afford tickets.
Korenhof remembered her husband, who she separated from a year ago, as a fun-loving and super-active person who was dearly loved by his friends and family.
"He was such a sweetheart; he had such a sweet heart," she said.
"We had our separation, but he was always there for the kids. And I'm so glad."
Asher was taking his dad's death hardest out of their two children, Korenhof said.
"They saw dad was sleeping and he wasn't going to wake up again.
"My son was really close with him and he needed his dad around to do dad things," she said, crying.
Jonathan's body was found on Wednesday last week, but because he had been living alone it was unclear when he died.
Korenhof said it was a reminder for diabetics to make sure they tracked their blood sugar levels and ate enough before bed.
While Jonathan was active and fit, he could sometimes be too casual about taking care of himself, she said.
She didn't want anyone else to die from preventable complications from diabetes, saying anyone living with the illness should remember to look after their health.
Back in Whakatane, friends and whanau were packing out Jonathan's family home, waiting for his arrival.
Going home for Christmas would be bittersweet, she said.
"We'll be back there to celebrate Christmas and New Years with our family, but under these circumstances."