A decade on, the bulk of the brothers' share of the inheritance is believed to have been lost through bad investments, while Arthur is in prison in Barbados, accused of masterminding an extraordinary, violent plot to kidnap his brother.
Four other men, all allegedly recruited from Gloucestershire villages, are also in custody on the island and, like Arthur Watts, face charges of kidnapping and wrongful concealment. Meanwhile, John Watts and his Spanish girlfriend, Annabelle DiEnjoy, 38, are recovering from an ordeal during which they were beaten and tortured.
The brothers' story is all the more remarkable because their father appears to have been the model of the respectable businessman, on the board of 60 firms and chairman of 16. He also held both private and commercial pilot licences and was a keen yachtsman, competing several times at Cowes week. At the age of 72 and after chemotherapy for leukaemia, he skied the men's Olympic course at Val d'Isère.
Both John, born in 1955 and Arthur, born 10 years later, were educated at their father's old school, Wycliffe College, near Stroud. In 1977 their mother, Phyllis, committed suicide; the writer Mary Lovell, biographer of the Mitford sisters and Sir Richard Burton, became their stepmother. She is believed to still live at the family mansion near Newport, south Wales.
A family friend said Arthur became a "party-animal and a charmer", who blew vast sums of money on partying. She said: "Arthur has never worked; he is just spoilt. He did what he wanted, until the money ran out." John, meanwhile, trained to be an accountant.
After their father died, the brothers decided to invest the bulk of their inheritance in the US; when the stock markets crashed after the 11 September attacks they lost very heavily. The friend said: "John took a gamble and it was the wrong one. They lost everything."
By now, John had moved to Barbados. From 2001, his younger brother is believed to have begun to claim that he was holding back a sum of money left by their father, said to be about £300,000. Those close to their family say on a previous occasion Arthur travelled to the island to threaten his brother and his former wife.
The family friend said: "John lived in fear of Arthur. He thought he was going to kill him. Arthur was convinced John had a secret stash of money." Arthur's latest and most serious attempt to force his brother to hand over money appears to have started last month, when he flew to the island with four other men: Damien Henson, 31, a plasterer, his brother, Adam Henson, 24, a chef, both from Cromhall, Stuart Williams, 25, a delivery driver from Thornbury and Jason Foster, 37. The men told their families it was "a lads' holiday".
The five are said to have flown to Barbados on 15 June. Then last Saturday two cars allegedly pursued John and Ms DiEnjoy along a road in an area called Church Village; some reports said the couple was forced off the road. They were forcibly removed from their car and driven to a house on the west of the island at the resort of Sunset Crest, where, family friends say, both were tortured.
Alerted by witnesses, police mounted a search, then were guided to the house by Ms DiEnjoy, who had been dumped in a field. Police raided the house, freed Mr Watts and arrested five men; both Mr Watts and Ms DiEnjoy were treated for their injuries in hospital.
After initial hearings, it is likely to be several months before the case comes to court; the five men are expected to remain in prison in the meantime.
Back in Gloucestershire, Yvonne Williams, mother of Stuart, said: "I believe he has been offered money to do something he would never usually do."
At her large rented home on the outskirts of Stroud, Arthur's wife, Jane, was under siege from the media. She would only say: "This has been a feud lasting five years and we want to sort it out in the family." Then she closed the door firmly.