In 1916, the novelist Thomas Mann wrote to his friend Ernst Bertram that he believed the tragedy of Germany was "symbolised and personified by my brother and myself". He may have been correct. The story of the strained relationship between Thomas and Heinrich Mann – characterised by a lifelong hate-envy – is a familiar part of German literary history. According to the German critic Marcel Reich-Ranicki, in his book Thomas Mann and his Family (1989), Thomas Mann "was as sensitive as a prima donna and as vain as a tenor". Reich-Ranicki hits exactly the right note: the Mann family story is the stuff of German opera.

Thomas and Heinrich were from Lübeck in northern Germany. Heinrich was the elder by four years. He dropped out of school, gave up work, and became a writer. His little brother Thomas wanted to be just like him. With the publication of his very first novel, Buddenbrooks (1901) – a fictional account of the Mann family – he succeeded. The book became a sensation. Thomas became rich and famous. "I was swept up in a whirl of success," he wrote. In 1912 he wrote Death in Venice and in 1929, he won the Nobel prize for literature. Meanwhile, Heinrich disappeared in his brother's wake.

Among his many works, Heinrich wrote only one novel that is now remembered, Professor Unrat (1905), and that only because in 1930 it was made into a film - The Blue Angel – starring Marlene Dietrich. Heinrich's books were not merely bad, wrote Thomas, but "bad in such an extraordinary way as to provoke passionate antagonism". "My brother-problem", he wrote in a letter in 1917, "is the real, in any case the most difficult, problem of my life ... At every step kinship and affront." Kinship and affront: not only Thomas Mann's themes as a writer, but the story of his life.

In 1905, Thomas married Katia Pringsheim and they had six children, despite the fact that Mann was gay, or rather, in Colm Toíbín's nice phrase, "gay most of the time". One biographer, Andrea Weiss, has argued that Mann did not care at all for Katia, only for her "cultured background, her family's position in Munich society, and no doubt the prospect of regaining the privileges of wealth which had eluded him since the death of his father".

His relations with his children were similarly complex. "When a man has six children, he can't love them all equally," Mann claimed. He loved the eldest, Erika, the most. She was an actor, and eventually became his assistant. Only one of his children, Klaus, became a novelist and he faced the same problem as Heinrich: how to compete with Thomas? He couldn't, and on 21 May 1949, in Cannes, he killed himself with an overdose of sleeping pills. Mann interpreted his son's death as a consequence of exile from Germany. But Klaus had faced other, more obvious challenges: he was a drug addict, he was gay and he was the son of Thomas Mann.

Another son, Michael, also killed himself (as did Mann's two sisters, and Heinrich's second wife). A third son, Golo, became an eminent historian, without a good word to say about his father. Only the two younger daughters, Monika and Elisabeth, seemed to have escaped their father's long, dark shadow.

On close inspection, great artistic dynasties often seem to be made out of other people's agony. Katia supported her husband, and raised their children at great personal cost. Late in life, she remarked: "I just wanted to say, I have never in my life been able to do what I would have liked to do."