"It's an unbelievable accident that has happened. No one knows what's going to happen next. It's so sudden," Mr Kadariya said.
"We're going to miss them for ever and ever. They will be in our minds and memories for ever. We will be trying our best never to forget them. It's the hardest time of our lives, ever."
Mr Kadariya flew to Christchurch today but is yet to see Mr Chhetri or the daughter who also survived the crash.
He understood Mr Chhetri had been moved from intensive care into a general ward at Christchurch Hospital but was unable to talk properly.
Mr Kadariya fondly remembered meeting Aron.
"He was gorgeous, with his smiley face at all times. He was happy at all times."
Mrs Chhetri was a "loving wife and caring mother", who was always friendly and generous to people.
She was also excited about the arrival of her son, who had three sisters.
The crash happened after the oldest daughter, Srijhana, 18, had been dropped off in Dunedin for university.
Friend and chairman of the Christchurch Bhutanese society, Akash Drukpa, said Mr Chhetri was a very careful driver.
"It's like a non-smoker getting lung cancer."
Mr Drukpa said the family was well known in Christchurch.
The community of 324 Bhutanese who had settled in the city would band together to help each other through the tragedy and was like a big family, Mr Drukpa said.
He said the Chhetri family was one of the first in Christchurch in the resettlement of refugees from a camp in Nepal. They were originally from the Bhutanese district of Tsirang.
"They took a bold step, moving to New Zealand, and many people followed them."
Mrs Chhetri was a "lively lady" who had a big heart, he said.
She worked as a caregiver in a Christchurch rest home, with her sister. Mr Drukpa said Mr Chhetri worked at a community college, and at other community groups as a liaison between the groups and refugee families who settled in the city.
"He was very well known in the community. It's going to be hard for him with his wife gone, and two babies."
Mr and Mrs Chhetri have three daughters. When Aron was born, Mr Drukpa said it was like an "exciting new phase" in the family's lives.
The Hindu family had celebrated Aron's first rice feeding on Friday, which Mr Drukpa had attended.
"It was a very auspicious occasion," he said.
The funeral for Mrs Chhetri and Aron would likely be tomorrow evening.The pair died at the scene of the crash, which happened on the Omarama side of the canal bridge on Twizel-Omarama Rd, State Highway 8, shortly before 7pm yesterday.
Five others were injured in the crash - including Mr Chhetri, who remains in hospital in a serious but stable condition, and their 10-year-old daughter, who is comfortable and will possibly be discharged today.
The three passengers in the second vehicle, travelling south, were transported to hospital - two by helicopter and one by ambulance.
The President of New Zealand's Non Resident Nepali Association, Baburaja Maharjan, said he was extremely saddened to hear about the accident, which claimed two members of Christchurch's Nepalese community.
Mr Maharjan said the family was returning home to Christchurch after visiting friends in Queenstown and Dunedin when the accident happened.The serious crash unit is investigating.
