I'm searching for the name of a book I've read over 10 years ago (so the book itself should be 10-15 years old) at my school library (in France but I believe it was translated from an American book).
The main character was a boy who discovered he could speak and understand every form of language in the world, be it simple Spanish in class (he discovered it first by becoming fluent and could answer the teacher with ease, without realizing he did it at first) or speaking to rats/insects or even fax machine.
According to LogicianWithAHat's comment, it was part of a series which then featured a girl with regenerative powers and another boy who could, among other things, see in infrared.
There might be something with aliens being the cause of it and they began to develop their power to fight them, but I'm unsure about that part (I never finished the series at the time). It's been a long time but I liked the idea of this apparently useless power which turned out to be actually very cool.