José “Pepe” Martínez Jr. was born in Guadalajara, Jalisco. When he was six years old, his father, Pepe Martínez Sr., joined Mariachi Vargas, and their family moved to Mexico City. At age seven, he enrolled in the Escuela de Iniciación Artística, where he learned piano and the fundamentals of music. Upon graduation, he continued his studies at the Conservatorio Nacional de Música and the Sindicato Único de Trabajadores de la Música.
At age 15, the newly formed Mariachi Juvenil Tecalitlán invited Pepe to join their group as a violinist, an instrument he had never played before. He promptly immersed himself in the study the violin, and from there went on to Mariachi Juvenil de México. In 1991, he joined Mariachi de América de Jesús Rodríguez de Híjar. Since 1993, he has been a member of Mariachi Vargas de Tecalitlán. His violin teachers were Salvador Torres and Antonio Ceballos, both accomplished violinists who were at one time Mariachi Vargas members, and he has had many vocal instructors.
Pepe Jr. received his initiation into arranging by working as a music copyist and analyzing the scores he copied, particularly those of his father and of Rubén Fuentes. Many of his arrangements have been recorded with Mariachi Vargas and other groups. In fall of 2013 his “Entre la Tierra y el Cielo” was performed with Mariachi Vargas and symphony orchestra at Guadalajara’s Teatro Degollado. Pepe’s advice to those who want to learn this music is “Devote yourself body and soul to your music. No matter what group you play in, you need to study instrument and voice, acquire musicianship skills, and be current with the repertoire.”