Three children are orphans after the death of the latest White Island victim.
Pratap Singh passed away at Auckland's Middlemore Hospital on Tuesday, a little over a month after the death of his wife Mayuri.
The Indian-born couple were both US citizens and lived in Atlanta.
Police on Wednesday confirmed the White Island death toll had risen to 21, with media in the United States naming Singh as the latest victim.
According to a message posted to Facebook by a friend of Singh's, the late couple left behind three children - an 11-year-old son and six-year-old twins.
Friend Swadesh Katoch announced the news of Singh's death "with a heavy heart and tearful eyes". He said Singh had a "short life but very well-lived".
Singh was president of Atlanta chapter of Sewa International, a Hindu faith-based humanitarian organisation.
"Pratap ji is very well-known for his philanthropic work in Atlanta, especially in the African American community in downtown area," Katoch wrote.
He added that Singh was a "self-made person who arrived in the US with no money, no degrees and no place to go, but made his name".
Singh suffered burns to 40 percent of his body in the December 9 eruption, while his wife had burns to 70 percent of her body.
Mayuri passed away in hospital on December 22.
Reacting to the news, friends paid tribute to the couple, writing they were "very generous and kind people", and expressing condolences for their children.
One friend wrote that Singh "left behind a great legacy of service, love and faith".
"[Pratap] was an energetic, witty and compassionate person...You left behind a great legacy in this world but a huge hole in our hearts."
