Despite the grim prognosis, the devastated koro said family were putting their faith in the doctors and God that he would have the strength, determination, and youth to recover.
"It is unfathomable that he is now fighting for his life - a circumstance we do not wish upon anyone."
He said his grandson and his friend were stopping off at their local for a "well-deserved" beer at the end of work a fortnight ago when the incident happened.
They were supposed to be joining whānau to celebrate his 75th birthday but never showed up.
The grandfather posted the friend was left with a number of injuries in the alleged attack but was recovering.
For the victims' privacy and because of the ongoing police investigation he was unable to reveal anything else about the incident.
The grandfather described his grandson as having "a warm and kind nature".
He said he was well known by his peers and family for his love and generosity of always putting others first.
"His genuine care and empathy is the reason why he has a huge support system during this hard time," wrote the grandfather.
The friend, who was also injured in the alleged assault, was a young, fit, hardworking father-of-two. He was like a second son to his daughter and considered family.
The grandfather said he had set up the page to financially help the victims, their partners and families during this time to help meet the loss of income and ongoing costs such as medical needs, treatment, travel and living costs.
Seven people have appeared in the Waitākere District Court variously facing charges including intent to cause grievous bodily harm, assault with intent to injure and injures with intent to cause grievous bodily harm.