"When people think of Dracula they think of handsome Bela Lugosi," said Holt, a gothic type wearing a T-shirt featuring the 1920s Hungarian actor heart-throb who starred in the first Broadway play based on Stoker's book, as well as the subsequent 1931 movie.
"Dracula was nothing like that. He was old and hunched over, had hair on his palms, and bad breath," Holt told AFP in an interview.
"He was out of the grave, he smelt like death," added Stoker. "We're going back to the original characters."
It was Holt -- whose passion for the theme stems from Francis Ford Coppola's 1992 "Dracula" movie -- who initially came up with the idea of a sequel to the Irish writer's 19th century work.
In search of data, he stalked descendants of the historical Transylvanian-born Vlad III Dracula of Wallachia, better known as "Vlad The Impaler", toured Europe on the vampire's tracks, met with scholars, and joined the Transylvanian Society of Dracula.
In 2003, he said, he came up with the idea of getting backing for a sequel novel from the Stoker family, who had lost the copyright early in the 20th century.
And Dacre, one of a score of close family scattered across Britain, Ireland, Canada and the United States, signed on. "He had Bram's genes and the name," said Holt.
From then on, the two worked together, studying notes left for the original work by Bram Stoker, writing the plot and building characters.
"We go back to the original but we don't leave it at that," Stoker said.
The sequel is set in 1912, 25 years after the finale of the first epistolary novel, as a series of chilling murders in London and Paris triggers a vampire hunt across Europe and unleashes terror of "the prince of darkness."
After careful analysis of 19th century notes left by Stoker, a theatre director who minutely researched background for the original novel, the two revived one of the old characters and added in a few, including a Scotland Yard detective and a lesbian vampire countess.
More significantly perhaps, Dacre Stoker also opted to throw his ancestor into the novel.
Why create a Bram Stoker character? "He was misunderstood, mysterious, no one knows why he wrote Dracula," the great-grandnewphew said. "He died without knowing the success of his iconic character. His life was a struggle."
Talks are under way to produce a movie version of the book, though the authors refused to say who with.
But if they have their say then Johnny Depp could play Dracula and Catherine Zeta-Jones star as the blood-sucking lesbian countess.