Mr Nevill's family now extends to seven generations and more than 100 of them, from New Zealand, Australia and the United States, marked the milestone during the weekend.
The reunion also celebrated the 140th anniversary of the family's settlement in the Ida Valley.
Relatives spent the weekend trading yarns about their ancestors; viewing family photographs, documents and objects on display; visiting the site of James' first home in the Ida Valley and some of the family farms and paying their respects at the graves of family members buried in the Omakau Cemetery.
"Historical information about your family is just the raw data. It's the people that bring it all alive," said Robbin Hepburn, of California; one of James Nevill's great-great-grandchildren.
Ms Hepburn and her sister Sally McKerchar, of Geraldine, said it was important to know your family roots and to pass on that information to your own children and grandchildren.
"History helps us know who we are and where we're going in the future," Ms Hepburn said.
They were enjoying catching up with a host of relatives and said one of the family traits that spanned the generations was "intensely blue eyes", with many family members sporting a similar eye colour.
Seven family members were the driving force behind the get-together - Peter Nevill, of Moa Creek, Lindy Nevill, of Mosgiel, Garth Nevill, of Waikouaiti, Trish Small, of Ashburton, Dorothy Nevill, of Mosgiel, Russell Nevill, of Moa Creek and the late Geoff Nevill, of Moa Creek.
Geoff Nevill, who died in March last year, had been excited about the reunion and very intent on making it happen, his family said.
The eldest descendant at the reunion, Angus Martin (92), of Oamaru, who cut the anniversary cake, said he had a "fantastic" time and enjoyed renewing his acquaintance with his cousins.
A flowering cherry tree was planted in the grounds of the Moa Creek Poolburn Memorial Hall to mark the occasion, with Garth Nevill and Ruby Wright, of Wellington, doing the honours.
Mr Nevill was the eldest male Nevill at the reunion, aged "in my late 60s" and 5-year-old Ruby represented the seventh generation of descendants.
James Nevill, born in 1836, was raised in Somerset, England.
He arrived in Australia in 1857 and joined the gold rush to Gabriels Gully in 1861, travelling around the Otago goldfields as a miner, later buying land and farming at Moa Creek.
He married Jane Torrance and five of the six children they had survived, with some of their descendants still living in the Ida Valley.
A book on the family history was planned, so those at the celebration were urged to record anecdotes and update family records.
A time capsule was buried in the hall grounds, with plans to unearth it in 50 years.
