Complex sentence: By that time, his hitherto relatively quiet life had been turned upside down by the death on of his older brother Dom José, which left John as the heir apparent to the throne with the titles of Prince of Brazil and 15th Duke of Braganza.
Split into simpler sentences: By that time his hitherto relatively quiet life had been turned upside down by the death on of his older brother Dom José. This left John as the heir apparent to the throne with the titles of Prince of Brazil and 15th Duke of Braganza.