Complex sentence: William III of Montferrat (it. "Guglielmo") (? -1191), also known as William the Old, was marquess of Montferrat from around 1136 to his death in 1191.
Split into simpler sentences: William III of Montferrat (it. "Guglielmo") (? -1191), also known as William the Old. He was marquess of Montferrat from around 1136 to his death in 1191.