The charges against the men, who have both pleaded not guilty, include murder, repeated beatings of prisoners and persecution of the Muslim population in the area.
The ugliest atrocities detailed in court documents are the deaths of around 140 Muslims in two separate torching incidents in which women, children and elderly men were burned alive in barricaded buildings.
Those who tried to escape the fires were shot by the cousins and their accomplices, the court alleges.
The incidents, in which 23 children ranging in age from two days old to 14 years perished, occurred within days of each other in June 1992.
Milan Lukic, who was arrested in Argentina in August 2005, was the leader of a Bosnian Serb paramilitary group known as the "White Eagles" and "Avengers", which included his cousin Sredoje, a former policeman.
Sredoje was handed over by Bosnian Serb authorities a month after his cousin's arrest.
'Reign of terror'
According to court documents, the reign of terror they unleashed in Visegrad was part of one of the most notorious campaigns of ethnic cleansing in the conflict, designed to permanently rid the town of its Bosnian Muslim population.
Before the war, Visegrad had a population of 21,000 inhabitants, two-thirds of whom were Muslim.
"Thirteen thousand Muslims were forcibly removed from their houses or killed during the period running from spring to summer of 1992," and the city "has the sad distinction of being second only to Srebrenica" as representing the largest population shift of the war, Groome told the court.
The atrocities carried out in Visegrad were "part of a larger plan" the prosecutor said, because of the town's "strategic importance" close to the border with Serbia.
Groome told the court that the "Lukic group" carried out beatings of Muslim prisoners "and in several cases tortured them with electric shocks".
Milan Lukic is also charged with shooting dead seven Bosnian Muslim factory workers on the banks of the river Drina on or around June 10, 1992.
Mitar Vasiljevic, a close friend of the cousins, was tried and convicted for his involvement in the same incident and sentenced in July 2004 to 15 years in prison.
Lukic was sentenced in abstentia to 20 years' imprisonment in Belgrade in 2003 for the murder, torture and abduction of 16 Muslims in Sjeverin in Serbia.
The bodies of the victims - passengers who were forced off a bus at gunpoint - were never recovered.