The recently discovered Brno manuscript BAM1 (Brno city archive. Manuscript collection, sig. 15/4) brings further understanding into the field of practice of 16th century music in Brno and introduces another research opportunities. The manuscript contains three polyphonic masses of less known composers Antoine and Robert de Fevin, belonging to the third generation of Franco-Flemish polyphonic. The study presents gathered biographies of both composers, however the major focus belongs to a hypothesis of fraternity of Antoine and Robert, not even excluding the possibility of duplicity of theirs identities. In this study are presented the results of the effected analysis of the composition style of the preserved masses Missa Le vilayn ialoys, Missa Ave Maria and Missa Helas ye suis mari, which is uniquely extant in BAM1 manuscript. These masses reflect the importance of Antoine and Robert de Fevin within the Franco-Flemish polyphony.