Writing Style Similarity Reflects Academic Genealogy

As authorship attribution systems are increasingly deployed to detect ghostwritten and AI-generated papers, their errors can support accusations against legitimate authors. These systems assume each author's style is their own. Researchers, however, study under advisors, and inherit their stylistic quirks. We build a corpus of arXiv authors with $\geq 2$ solo papers from the Mathematics Genealogy Project graph, giving $5{,}803$ total authors and $2{,}501$ ground-truth advisor-student pairings. Using embeddings from a fine-tuned model, advisors sit $39.9\\%$ closer in cosine distance to their students than a random same-field author does. Two open encoders reproduce the effect at $12.6\\%$ and $14.5\\%$. Academic siblings, two students of one advisor who may never have met, sit $30.4\\%$ closer across $8{,}360$ pairs, even when they studied at different institutions. Pairs who share only an institution and a field show negligible similarity. Given a closed-set attribution task over the same corpus, the system's errors occur on the true author's advisors, students, academic siblings, and lab mates $11$ times more often than chance.