I am trying to identify a children's fantasy book I borrowed at the library at around 10-12 years old (early 2000s). The story was in French but it might have been a translation. Below are the elements of the story I recall:
It is the story of boy, of around 10 years old I think, who has a teenage sister. Their parents died in a boat accident some time ago and were cousins (their family was against their marriage).
The story takes place in a world with less advanced technologies than in our world. I remember that there are no cars. There exists some kind of magic and the boy thinks his sister is a witch. But we learn that in fact he is the wizard and she stole his magical abilities.
There exists several parallel worlds and our world is one of them. Every characters have an alter-ego in each world.
The sister went into another world where she is treated like a queen. I think that she had to switch places with her alter-ego from another parallel world that replaces her in the world she left.
The boy meets the alter-ego of his sister from our world and discovers that his own alter-ego died at birth. At some point he comes into our world and is sick during a car ride.
The boy had a total of 9 lives, represented by matches in a box. Several of them are burnt:
- one for his death at birth
- one for his death in the boat accident that killed his parents
- I think one that his sister took to steal his magical abilities
- one when he lights it, not knowing it is special
I can't remember the name of the characters.