Auckland's Buttle family owns Whakaari/White Island, one of a few privately-owned islands throughout New Zealand, property records show.
The title shows their company, Whakaari Trustee, as the registered landowner.
Companies Office records show three shareholders: James Buttle of Shortland St in Auckland CBD, Andrew Buttle of Greenhithe and Peter Buttle of Mission Bay.
• White Island volcano erupts in Bay of Plenty: 5 dead, 8 missing, 31 in hospital
• White Island erupts: Dramatic moment Whakaari/White Island volcano erupts
• White Island eruption: US couple on honeymoon suffered severe burns, parent 'livid'
• 'Indescribable': A tourist documents hell unfolding on Whakaari/White Island
They each own a third of the shares in the company giving them an equal and undivided third of the island.
All three men are also the company's directors. The company was registered in 2008 and property records show the title to the 237ha island was issued in May, 1935.
James Buttle said this morning: "We are devastated. One brother is in Whakātane. A statement will be issued shortly."
Those who know the family say they have a great affinity for the island they have inherited, as well as for the sea.
James Buttle was on the island recently and is also the commodore of the Mahurangi Cruising Club.
Peter Buttle is on the philanthropic Edmiston Trust Board.
Andrew Buttle has said he and his brother Peter once camped on the island, helping with research on muttonbirds.
The men's mother, Beverley Buttle, aged 91, said today: "We really have been very hard hit by this. There's nothing the family can do."
She recalled staying for one night on the island in the 1960s with a Rotorua tramping club which had boated out from Tauranga.
"We slept in the old factory. It's all disappeared now." Few people visited the island back then, she said and during her many visits, the volcano was relatively quiet.
Tour operators paid the family business a royalty to visit, she said, and she received a share of that.
"They pay me a retainer."
The family planned to keep the island and Buttle cited a number of grandchildren.
"It will stay in the family. It's most unusual to own a volcano. People always found it fascinating to visit," she said.
In 2014, the Herald reported how 100 years ago, 10 sulphur miners had died on the island when they were swamped by an avalance of volcanic debris.
Whakaari/White Island was first visited by the Māori in the early 1800s, who fished and caught muttonbirds, often cooking them in the steam from the crater vents, the Herald's 2014 story said.
The island has changed hands frequently since 1861 when it was thought to be sold by a Bay of Plenty chief to a European for "two hogshead of rum".
The NZ Sulphur Company was wound up in 1934 and an Australian syndicate bought the island to produce salt "using fumaroles for the evaporation of seawater".
That plan evaporated and the island was sold to an Auckland sharebroker, George Buttle, in 1936. It has been in the Buttle family ever since. Buttle decided not to develop it.
The island passed to his son, John, who passed it on, in trust, to his three sons, James, Peter and Andrew.
Andrew Buttle says he and his brother Peter once camped on the island, helping with research on muttonbirds. By day, the island was deserted, he says, but at night muttonbirds would come "crashing in" under the pohutukawa trees.
"We'd take blood samples after dark. You could walk right up to them and pick them up."
Whakaari/White Island is protected, as are its muttonbirds and gannet colony. Tour operators say they use trails near waterways so that during the next rain, footprints will be washed away.