I vaguely recall that one of the later books dealt with a reunion of the Quiz Kids (I'm mostly sure that was the name of the show, but I could be wrong) in some kind of competition. Jupe was pressured into playing dumb and losing, although the exact details elude me.

I'm pretty sure they didn't go *that* deeply into backstory, other than raised by his aunt and uncle. This fits with what we saw of Matilda, who was fond but firm.

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