He served as a lawyer and licenciate, Alcalde del Crimen (Magistrate of Crime) in the Real Audiencia and Chancery of Granada, a prosecutor and a Minister of the Council of Orders.

[7] His paternal uncle, Diego López de Medrano y Vinuesa, served as Mayordomo Mayor to Empress Isabella of Portugal, wife of Charles V, Holy Roman Emperor.

Diego's second son, Francisco de Medrano, held the position of royal accountant and treasurer for Charles, Prince of Asturias.

[8] On 1 September 1552, Charles V, Holy Roman Emperor, issued the Carta Ejecutoria de Hidalguía to confirm the noble status of the Medrano family.

[1] According to genealogical proofs provided by García de Medrano y Castejón, this branch of the family not only owned the entailed estate and fortress of San Gregorio but also possessed 15,000 sheep.

[10] Their livestock grazed in those lands, and hundreds of times they walked to the pastures of Extremadura or the royal valley of Alcudia, in La Mancha.

He graduated with a bachelor's degree in Law and was subsequently admitted to the prestigious Colegio Mayor de San Bartolomé of Salamanca on March 1, 1573.

[3] During his time at the college, he demonstrated exceptional academic skill, quickly obtaining a licentiate degree and a PhD in Law.

[3] According to The History of the Old College of San Bartolomé, as noted by Ruiz y Vergara in Volume II, page 407: Don García de Medrano, a native of San Gregorio..., son of Don García de Medrano and Doña Cathalina Castejón, was received on March 1, 1573.

On the street of the jail, he saw canopies hanging in front of the dwelling of Don Pedro de Granada y Venegas, on whose sides were the coats of arms and coronets of this royal house.

After officers of the court and other people had pacified them, that very day Don Alonso went to the bishop to complain to His Majesty of this offense against his nobility and his blood, [recalling] the many honors and favors and privileges that he had received from the Catholic Monarchs and the Emperor Charles V, who used to write to the grandfather of this noble gentleman and call him cousin.

[29] On page 14, García de Medrano y Castejon himself explains: "In compliance with the order of the Chapter, I reviewed all the laws of this book with great care and diligence, removing those that were no longer necessary, and in others, according to the changing times, increased the penalties for offenders.

All the laws of the Kingdom, which say the same thing, were put in place for my temporal governance, and for the spiritual, what was established in the Holy Council of Trent was also included: all of which was seen and approved in the said Chapter.

"[30] Philip III of Spain himself writes: "the obligation We have to order and which pertains to the good governance of our subjects (to which with the help of God we strive to attend in all parts) calls us particularly to comply with much care in what concerns the good state of the Military Orders and to maintain as we do in their administration, care of the spiritual and temporal; and being as they are Religious Orders...it is of greater service to our Lord to preserve them in their good state and strive for them to grow in virtue and religion..."[31] King Philip III of Spain was the administrator of the Order of Chivalry of Santiago by Apostolic authority, he agreed to make some new establishments, and to smooth and correct some of the old ones, and leave the others as they were, and from all of them, to make a book, entrusted to García de Medrano y Castejon, to compile everything into one book in the form that follows, mandating, as he expressly command, that the said establishments contained in this book be kept, fulfilled, and executed with complete punctuality, according to God and the Order of Santiago.

According to Barrientos Grandón, this marriage was the root and origin of one of the most extensive families of legal professionals in the service of the Monarchy during the 17th and 18th centuries.