Funny little mystery — the phrase 'my brother idiot' could be coming from several places in a novel series, and tracing it is half detective work, half fandom archaeology. When I try to pin these things down, I usually start with the obvious: look for the first chapter where that line appears in context. Often it’s either a recurring joke the narrator uses to describe a sibling, or it’s a blunt tagline the translator picked for a chapter heading or blurb.
If the series was translated, translation choices can easily create memorable short phrases that fans latch onto. Check translator notes, chapter titles, and the original-language opening lines. I’ve found gold in authors’ afterwords and translator comments on sites like forum threads or hosted chapter pages — they sometimes explain why they chose a specific rendering. If that fails, searching quotes in quotation marks on search engines, checking fan translations, and peeking at archived pages usually reveals when a phrase first popped up. It’s a satisfying little hunt, and often you discover other quirky translation decisions along the way.