Complex sentence: Her place in his affections was filled by the beautiful Giulia Farnese, wife of an Orsino Orsini, but Alexander VI's love for his children by Vannozza remained as strong as ever and proved, indeed, the determining factor of his whole career.
Split into simpler sentences: Her place in his affections was filled by the beautiful Giulia Farnese, the wife of Orsino Orsini. However, Alexander VI's love for his children by Vannozza remained as strong as ever; it proved, indeed, the determining factor of his whole career.