Nephew of Simeon of Coucy-leChâteau and of Jacob of Corbeil; flourished about 1200. In 1227, after having compared all the copies of the French Maḥzor he could obtain, he wrote the Maḥzor, Code Uri, No. 225, to which he added a commentary consisting chiefly of compilations of written and traditional explanations from his uncle Ephraim ben Menahem, and from Shemaiah bar Isaac, Moses ben Kalonymus ha-Zaḳen, and Meshullam bar Simson ("Cat. Bodl. Hebr. MSS." No. 1206). Neubauer thinks that MS. No. 1209 in the same collection is a shorter form of the same compilation. Aaron seems to have known some Arabic, and quotes French and German words.