It began August 30, 1498, when Caesar was still a cardinal.

In this letter, which is written in Latin, he announces to the duke that he is about to set out for France, and asks him for a saddle horse.
Caesar engaged in an equally confidential correspondence with Francesco Gonzaga, with whom he entered into intimate relations which endured until his death.

In the archives of the Gonzaga family in Mantua there are preserved forty-one letters written by Caesar to the marquis and his consort Isabella.

The first is dated October 31, 1498, from Avignon; the second, January 12, 1500, from Forli; the third is as follows: ILLUSTRIOUS SIR AND HONORED BROTHER: From your Excellency's letter we have learned of the birth of your illustrious son, which has occasioned us no less joy than we would have felt on the birth of an heir to ourselves.

As we, owing to our sincere and brotherly goodwill for you, wish you all increase and fortune, we willingly consent to be godfather, and will appoint for our proxy anyone whom your Excellency may choose.