Beethoven was deaf and so of course must have had someone else write his music for him, but who that someone was we may sadly never know. I suspect though that it was Mozart, who presumably faked his own death to escape his creditors and possibly also the murderous intent, real or imagined, of Salieri.
This you might argue is all a bit speculative, where is my proof, etc. My ears are my proof, and Beethoven, lest us not forget, didn't have any any - ears that is, in the practical sense. That is of course yes naturally he did have ears, but they were not practical.