Enslaved by pirates

Perhaps the most famous pirate slave in history was the Spaniard Miguel Cervantes, who was captured by Memmi Reis after the Battle of Lepanto. He tried to escape four times, but was eventually released with the help of the Redemptionists, who paid 500 gold escudos for his life.
Cervantes went on to become famous as the author of Don Quixote de la Mancha ("The Man of La Mancha"), which includes a story about slavery, called 'The Captive's Tale'.
Famous fictional pirate slaves (besides, of course, Lily Swann and Carlo, in Swashbuckler, who aren't treated that badly - at first) include Sir Oliver Tressilian in Rafael Sabatini's novel The Sea Hawk. Sir Oliver is betrayed by his own brother, sold into slavery, but ends up becoming one of the most notorious Barbary corsairs.
On the other hand, in Captain Blood, Sabatini's hero Doctor Peter Blood is sent by an English court as a slave to Barbados. He escapes from there and becomes a pirate, and later buys his sweetheart, Arabella, from a French pirate who has captured her.
You might have seen the movie of Captain Blood, with Errol Flynn and Basil Rathbone - it's one of the first great swashbuckling films.