Story of a wizard boy with 9 lives

Question

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.

Answer 1

This is Charmed Life by Diana Wynne Jones.

The wiki summary matches the details you have given, such as orphaned children and magic:

When the Chant children, Gwendolen and Eric "Cat," are orphaned after their parents die in a boating accident,Gwendolen petitions Chrestomanci to let them live at Chrestomanci Castle where she can further her magical training.

More on Gwendolen:

Gwendolen is extremely ambitious and has master plans to be Queen or to rule the world.

Gwendolen is replaced by a lookalike:

The next morning, Gwendolen has disappeared and a confused lookalike named Janet has taken her place.

The lives = matches detail matches as well, which our hero definitely didn't know were special:

Janet discovers a book of nine matches, five of which are already burnt. When Cat foolishly strikes a match and finds himself engulfed by flames, Janet's suspicions are confirmed: Cat, who has always believed himself utterly lacking in magical ability, is actually a nine-lived enchanter.

So yes... Cat has nine lives... and is magical.

And his sister has indeed been stealing his magic:

Gwendolen has been leeching Cat's magic and wasting his lives to fuel her own magic.

The breakdown of his lives and deaths are as follows:

He only has three lives remaining, having lost

• the first life when he only just survived being born
• the second when Gwendolen put his lives into a book of matches (to make them easier for her to use)
• the third when he drowned in the boating accident that killed his parents
• the fourth when Gwendolen used it to turn his fiddle into a cat (which he kept as a pet and named Fiddle)
• the fifth when Gwendolen used it to take her into her new world where she reigned as queen
• and the sixth when he burned a match from his 'life book' of matches in an attempt to prove that he didn't have nine lives and the matches weren't connected to him

Also worth noting:

Dutch and Finnish-language translations were published in 1980, followed by German. Danish, Italian, and French editions were published in the 1990s (when the four early novels were in print); later Polish and Spanish, Chinese and Vietnamese, Serbian.