It sounds like an unlikely plot in the prelude to the Second World War – German "twins" end up on opposing sides, one a German officer and the other fighting for the British army.
But that is the basis of writer and comedian Ben Elton's latest novel, Two Brothers, a fictional tale inspired by Elton's own family history which saw his Jewish father's adopted cousin fight in the Wehrmacht during the Second World War while his uncle was fighting for the British Army.
With 13 best-selling novels and four hit musicals to his name, the 53-year-old multi-millionaire co-creator of Blackadder is keen not to talk solely about his family history, even though he concedes it's fascinating.
Elton's father, Ludwig Ehrenburg, was born in Germany into a secular family of Jewish descent. With his parents and older brother Gottfried, he came to Britain in 1939 via Czechoslovakia, where his father worked as a professor of ancient history at Prague University.
The two boys had experienced anti-semitism in the Thirties, before the war began, Elton explains.
"In the German schools they went Nazi before Hitler came in. They (his father and uncle) were insulted by Nazi teachers and witnessed the confusion of the so-called Mischling (the German term used during the Third Reich to denote persons deemed to have only partial Aryan ancestry).
"My father's best friend was half Jewish and, on being given a chance, elected to sit with the Jews. He did not survive the war."
Through his academic connections, Ludwig's father secured a research position in London and the family escaped Prague in 1939, a month before Hitler occupied the city.
Their adopted cousin, Heinz, who, to use the Nazis' own term, was of pure "Aryan" blood, decided to stay to be a farmer, but was soon drafted into the Wehrmacht.
"People think, does that mean you had a Nazi in the family? Well, no, of course not," Elton reflects. "Heinz was an ordinary German who became a farmer caught up in a geo-political situation like many other people and was drafted into the Wehrmacht and, short of allowing himself to be shot, he didn't really have much choice."
When Gottfried enlisted in the British Army he was told to anglicise his name in case of capture by the Germans so he became Geoffrey Elton while Ludwig became Lewis Elton.
Later, it turned out that Heinz and Geoffrey actually came quite close to each other while fighting on opposite sides.
"The fact that both cousins survived and were able to be friends afterwards is the best part of the story," says Elton.
Only his father's side of the family are of Jewish descent, he points out, but some of them died during the war, including his grandmother's sister, who was shot accompanying a group of Jewish children being transported east. The children were also killed on arrival in Lithuania.
Elton has known about the family history for a long time but has been reluctant to ask too many questions.
"My experience of people who've lived through difficult times is they're not as anxious to talk about it as those who've been lucky enough not to live in difficult times are to hear about it," he explains.
While the novel follows the story of two babies born in Berlin in 1920 – one Jewish, the other adopted, but both raised as twins unaware of the adoption – it is clear from the outset that under Nazi rule the truth will lead to very different fates for each boy.
And while the author builds a terrifying picture of persecution of the Jews, he tries to remain optimistic about future generations.
"I believe that in the long run the human capacity for good is greater than the human capacity for evil, and that the fact that humanity can love, can, and will, be its salvation.
"People tend to be generally good. It's only when they get into crowds that they start to act badly."
But he believes it's important that future generations are not allowed to forget the Nazis' atrocities.
"It's only three generations ago. The institutions that the Nazis corrupted were noble institutions, all of which we rely on today – the courts, the police, the civil service and the medical service."
Although he is half-Jewish by birth, Elton is an atheist.
He grew up in south east London and didn't know the word Jew until he was about 10 because his family wasn't religious. His mother was brought up in the Church of England.
He made Australia his permanent base three years ago, settling in Fremantle, near Perth, with his wife, Australian saxophonist Sophie Gare, and their three children, Fred, 11, and twins Bert and Lottie, 13.
They also have a home in Sussex and are spending time in England while he's writing a new BBC family sitcom called Slings And Arrows.
"While the kids are growing up, I don't want to go on the road for months, but I will again for comedy tours," he says.
Two Brothers by Ben Elton is published by Bantam, priced £18.99. Available now