Complex sentence: Two years later she began to have a love affair with Fabrizio Carafa, the Duke of Andria; evidently she was able to keep it secret from her husband for almost two years, even though the existence of the affair was well-known elsewhere.
Split into simpler sentences: Two years later she began to have a love affair with Fabrizio Carafa, the Duke of Andria. Evidently, she was able to keep it secret from her husband for almost two years, even though the existence of the affair was well-known elsewhere.