Fray Gabriel Téllez, the Mercedarian priest known as Maestro Tirso de Molina, is purported to have handed publishing responsibilities to a nephew, Francisco Lucas de Ávila, naming him the compiler of his plays in Partes beginning in 1634. Scholars have debated whether the nephew lived in the world or only in the dramatist’s imagination. Since to date the only real traces of the man called Tirso’s nephew are found in the preliminary material of Partes II–V of Tirso’s plays, those pages are the focus of interest: the title page of Partes II–V (1634–36) lists him as the plays’ compiler; the prologue and dedication to Tirso’s Parte III (1634) are written under his name, indicating that he is now in charge of publishing his uncle’s plays; and the suma del privilegio of Parte V, dated July, 1635, authorizes him to publish that volume for a period of ten years. Before considering the fragments of Francisco Lucas found in the preliminary matter, it is fitting to provide the setting of his arrival on the scene in 1634 by reviewing some relevant facts of Tirso’s life and the publication history of the five Partes. The results of studying the texts of the prologues in the context of the Partes’ chronology add substance to the contention that the nephew never existed.