Philippe Grimbert: Un secret (2004)

The narrator of the partly autobiographical novel Un secret was originally called Grinberg, which obviously reveals the Jewish name. He grows up a weakling at the side of his athletic parents, and as he's without a brother he obsessively invents one. His parents Maxime and Tania run a clothes shop in Paris, with Louise (also a Jew) running a shop above them.

One day Louise tells the narrator the story his parents haven't told him, what has been kept a secret from him. His mother Tania was once the sister-in-law of Maxime, who was married to Robert, and Maxime was married to Hannah and they had an athletic son called Simon: yes, the narrator had a half-brother, no need now to invent a brother.

The Nazis killed Robert, Hannah and Simon, and in time (and not without a huge amount of guilt) Maxime married the beautiful Tania: they have loved and lusted after each other for so long that, tacitly, everyone agreed it was bound to happen.