Prospero was Duke of Milan 12 years ago. Fascinated by his studies, he turned over his day-to-day power to his brother Antonio, who made a deal with Alonzo, King of Naples. In return for tribute from Milan to Naples, Alonzo helped Antonio depose his brother. Prospero and his 3-year-old daughter Miranda were set adrift on the sea, which stranded them on an island all these years.
They survived and Prospero continued his studies, becoming a powerful magician. He recruited a magical servant, Ariel, and tamed the savage Caliban, the island’s only human (sort of!) resident, to do his bidding. Most importantly, he raised his beautiful daughter.