He is the first-born son of Pope Alexander VI and Vannozza de Catanei according to his contemporary, the famous Italian historian Francesco Guicciardini. The latter's statement regarding Juan Borgia as the first-born son was confirmed by Ferdinand Gregorovius, who spent many years in the archives of Rome and has been regarded as one of the great Borgia experts.
Lucrezia Borgia – The Life of a Pope's Daughter in der Renaissance
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