Complex sentence: Their oldest son was Count Giulio (1532-1571) died while he was Cuirassier for Guido Ubaldo della Rovere, the Duke of Urbino and General of the Venetian army.
Split into simpler sentences: Their oldest son was Count Giulio (1532-1571). Giulio died while he was Cuirassier for Guido Ubaldo della Rovere, the Duke of Urbino and General of the Venetian army.