e Castro was born ca. 1540/45. His birth place is not yet known for certain. However, evidence strongly suggests that he came from the Land of Liège.
First, the title page of De Castro's Novae cantiones sacrae from 1588 the composer describes him as "Eburone", a term which was frequently used in the 16th and 17th centuries to indicate a native from Liège.
Secondly, De Castro dedicated the Novae cantiones sacrae from 1588 to Ernst of Bavaria, Archbishop of Cologne and Prince Bishop of Liège. It is in his position of Prince Bishop of Liège that Ernst is refered to systematically as Prince of "Eburone" in a volume of odes mostly written by the poet Jean Polit.
Thirdly, Jean Polit, who was from Liège himself, was well acquainted with De Castro: in 1588 he wrote a poem in praise of the composer which opens the above-mentioned motet book for Ernst of Bavaria; he was probably also the one who introduced De Castro to the court of Ernst in Cologne in those years.
Moreover, an ode in De Castro's chanson anthology La fleur des chansons à trois parties (Louvain-Antwerp, Phalèse-Bellère, 1574), written by an author from the Southern Netherlands, Etienne De Walcourt, refers to the composer as "nostre Castro".
Finally, De Castro dedicated one of his first volumes (a volume of chansons and madrigals of 1577) to another famous Liège inhabitant, Gerard of Groesbeck.