Some were forced to squat in woods behind their living areas, while electricity was “dangerously” tapped from a nearby pylon.
Judge Timothy Spencer QC told the head of the family, Martin Rooney Senior, that the gulf between the lives of his relatives and their workers was “like the gulf between medieval royalty and peasantry”.
One man had been working for the family for 26 years.
While the gang members lived in luxurious homes, bought high-performance cars and enjoyed holidays to Barbados and cosmetic surgery, their slaves were kept in squalid caravans or kennels, with little access to heating, water and toilets.
The group were reported to bet on football, but not matches they were involved with.
As their betting became more serious, Owen was said to have found the bets too large to handle and introduced his colleagues to Mr Smith's bookmaking operation.
Members of the gang sought out targets in the streets, hostels and shelters, offering work for food and accommodation at sites in Drinsey Nook and Washingborough, then used false promises, drugs, alcohol and violence to entrap them.
Many of the victims, aged between 18 and 63, were homeless, while others had learning disabilities or complex drug and alcohol issues.
Some of the Rooneys also targeted four elderly homeowners, getting them to sign over properties into their names and selling three on for profits of up to £250,000.
Chief Superintendent Chris Davison, Head of Crime for Lincolnshire Police, said: “The severity of these crimes is underlined by the sentences imposed by the judge.