Son of Juan Alonso de Guzmán, VI Duke of Medina Sidonia and Ana de Aragón. He was IX Conde de Niebla but never became Duke of Medina Sidonia because he died before his father.
Gómez Fernández quotes the chronicler Barrantes Maldonado who confirms his name resulted being born on the feast of Santa Clara, and praises his many cultured attributes. In 1541 he married doña Leonor Manrique Sotomayor, daughter of the dukes of Bejar, Francisco de Zúñiga y Sotomayor and doña Teresa de Guzmán y Zúñiga.
There is documentary attestaion to the fact that he played vihuela, lute, and that he owned cornettos. It is not beyond possibility that he was the “claro Guzmán” the first mentioned by Bermudo (Bermudo 1555, fol. 93v): “Alaban por cosa particular al claro Guzmán, que tañía en vihuela desta manera destemplada.” (Claro Guzmán is praised for his particular ability in playing this scordatura fashion)
These are the music-related facts:
1538-1539 —He attended de Cortes of Toledo and would have met Luis de Narváez, and Mudarra
1542, 19 November — inventory of his possessions lists two vihuelas and a cornetto in his chamber.
1542, 12 October pays a violero named Castillo for repairs: stringing and “el adobyo de dos biguelas”
1545, buys vihuela strings