Martin Hollander, 48, and his wife Barbara, 50, from Sydney's North Shore, are believed to have died.
Their two teenage sons, Berend (known as Ben) and Matthew Hollander, students at Sydney high school Knox Grammar, died in hospital earlier this week.
In a statement supplied to ABC Eyewitness News Chicago and shared with news.com.au, Barbara's parents Larry and Norma Noesen confirmed they had lost hope the couple would be found alive.
"We are together with our family grieving the loss of our loved ones. Our amazing daughter Barbara Hollander and our son-in-law Martin Hollander were a wonderful couple and parents to our grandsons, Ben (16) and Matthew (13)," the couple said.
"We appreciate all the support and contact from our friends and family. During this trying time we ask for privacy as we process all the tragic events that have occurred. A memorial service will be planned for the summer/fall of 2020."
North Sydney family Anthony Langford, his wife Kristine Langford and their 17-year-old daughter Winona are all missing but feared dead.
Winona's aunt took to Facebook to say authorities "don't believe … they have survived".
Anthony and Kristine's son Jesse, 19, survived the eruption and is in hospital severely burned.
Krystal Browitt, a 21-year-old studying veterinary nursing, is still missing.
She was on the cruise ship Ovation of the Seas to celebrate her 21st birthday with her family.
Her father Paul was medevaced to Melbourne on Thursday morning, her older sister Stephanie is in a New Zealand hospital with severe burns and her mother Marie, who decided not to go on the volcano tour, is awaiting news.
AUSTRALIANS IN HOSPITAL
Jesse Langford, 19, is in hospital with severe burns. According to the aforementioned Facebook post, it's believed the Sydney teenager has lost both his parents and sister in the eruption.
Lisa Dallow, 48, has been flown to Melbourne to receive treatment at The Alfred Hospital's special burns unit. She has 57 per cent burns to her body and internal injuries. Her husband Gavin, 52, and daughter Zoe, 15, were killed in the eruption.
Paul Browitt, whose daughter Krystal is believed to have died, was also flown to The Alfred Hospital yesterday morning for treatment.
His 23-year-old daughter Stephanie is in a hospital in Christchurch with severe burns. Her uninjured mother is by her bedside.
Nick and Marion London, a couple from Engadine in Sydney's south, are also in hospital.
AUSTRALIANS CONFIRMED DEAD
Julie Richards, 47 and her 20-year-old daughter Jessica were confirmed dead yesterday. The mother and daughter, from Brisbane, had a love for cruising and had been on the day trip from Ovation of the Seas when the eruption killed them.
Gavin Dallow, from Adelaide, was killed by the volcano. His 15-year-old stepdaughter Zoe is believed to still be on the island but presumed dead.
Richard Elzer, 32 and Karla Matthews, 32, are also confirmed dead.
The high-school sweethearts, from Coffs Harbour on NSW's Central Coast, had been travelling with a group of friends on the cruise ship.
Their friend Jason Griffiths, 33, died in hospital after suffering severe burns. Other friends, who had been travelling with the three, are at the bedside of another severely burnt friend, believed to have burns to 80 per cent of his body.
The final two Aussies confirmed dead were the Hollander brothers from Sydney.
Berend, 16, and Matthew, 13, both died in hospital from severe burns to their bodies. Their parents, according to the statement above, are believed to have died.
OTHER COUNTRIES AFFECTED BY THE ERUPTION
Two New Zealand tour guides tragically died in the eruption.
Hayden Marshall-Inman had worked for White Island Tours for years before he was killed by the volcano. Tipene Maangi also died.
Two more Kiwi guides, Kelsey Waghorn and Jake Milbank, was badly burnt in the eruption. They are both fighting for their lives.
German woman Angelika Westenfelder, 63 and her husband Horst, 63, are still missing.
Two Americans Lauren Urey, 32, and her husband Matthew, 36, are in hospital with severe burns. They were in New Zealand on their honeymoon.
Another American couple, Ivy and Rick Reed, are believed to be in hospital with severe burns.
NATIONALITIES CAUGHT IN THE WHITE ISLAND ERUPTION
5 New Zealanders