Patrick Joseph Connors, 59, Patrick Dean Connors, 39, William Connors, 36, and Lee Carbis, 34, deny a number of offences.
They are accused of keeping Michael Hughes, now 46, and another man, 41, in "appalling conditions" in south Wales and paying them just £10 a day.
On Tuesday, a jury heard the pair were "hunted down" whenever they escaped.
Prosecution counsel John Hipkin said Patrick Joseph Connors ran a driveway tarmacking and building firm, with much of the work illegally targeting "vulnerable" victims using "inflated" prices.
The two men were allegedly forced to work for the business over a number of years and were beaten or threatened if they did not do as they were told.
They were paid £10 a day or in alcohol and tobacco, living in "appalling conditions" in a shed, garage and tin hut without access to heating or water, the prosecution said.
"They were denied basic self respect and called dossers and told if they were killed that they would not be missed," Mr Hipkin said.
"If they tried to escape they would be hunted down and brought back."
Mr Hughes, originally from Aberdeen, spent more than a quarter of a century under the men's control, prosecutors said.
The second victim, who cannot be named and was referred to in court as Mr K, tried to escape four times and even jumped from a moving car during a failed attempt.
When interviewed by police, Patrick Joseph Connors said he had never committed any offences against the two men, insisting he had paid Mr Hughes well.
All four defendants deny one count of requiring another person to perform forced or compulsory labour between 2010 and 2013.
Patrick Joseph Connors, of Rumney, Cardiff, has also pleaded not guilty to eight counts of causing actual bodily harm, four of kidnap and one of conspiracy to kidnap.
Elder son Patrick Dean Connors, of Rumney, denies kidnapping and conspiracy to kidnap.
William Connors, also of Rumney, has pleaded not guilty to causing actual bodily harm on a man between 2009 and 2013.
Patrick Joseph Connors' son-in-law Carbis, of Trowbridge, also denies one count of kidnap between 2001 and 2002.
The trial continues.
A man was forced to spend 26 years doing heavy labour for tiny sums, Cardiff Crown Court has heard.