Now 1623 was also the year two actors first published a folio edition of the work of William Shakespeare, and that edition contained a list of "The Names of the Principall Actors in all these Playes." However, that list didn't tell readers which actor had played which role.
quarto edition of The Duchess of Malfi lists "The Actors Names" it actually gives the play's characters followed by which actor played each part. According to the play's title page, the piece had been performed both at the indoor Blackfriars Theatre as well as at the outdoor Globe. It also appears to have been performed in different years, since some roles list two different performers, the first one generally a bit older than the second.
Only one actor, however, is listed for the title character, and that is R. Sharpe, presumably Richard Sharpe, who was born around 1602, and so would have been only about 12 years old when the play premiered (before the end of 1614). The second set of actors appear to have taken over their roles sometime after the death of Richard Burbage in 1619. So if we hypothesize a revival around 1621, Sharpe would have been only about 19 then, still young enough to play female roles in the Jacobean theatre.
While little is known about the life of Sharpe, there is a wealth of material about his co-star in the premiere of The Duchess of Malfi, Burbage. Known for such roles as Richard III, Hamlet, Othello, and King Lear, Burbage played the character of Ferdinand, twin brother to the Duchess of Malfi. The twins' younger brother, a Cardinal, was initially played by Henry Condell, who was one of the two actors who compiled Shakespeare's First Folio. While he lived until 1627, he might have taken on more of a managerial position in the company later on, and he was replaced in his role by Richard Robinson. Joseph Taylor replaced Burbage as Ferdinand, and both Taylor and Robinson were listed as "Principall Actors" of Shakespeare, as well.
One of the most curious things about the quarto of Webster's play is that it first lists Bosola, a comparatively lower-class character who would generally be placed after the upper-class folks. However, Bosola is a central figure in the play, and he was apparently quite competently played by John Lowin (listed in the First Folio as "John Lowine"). Known for playing the title characters in Shakespeare's Henry VIII and Ben Jonson's Volpone, Lowin might have distinguished himself so well in the part of Bosola as to earn top billing for himself.
Antonio, who marries the Duchess in the first act, was initially played by William Ostler, who died in December of 1614. (That's how we know the play must have premiered before then.) He was replaced by Robert Benfield.
It is the Duchess herself, however, who fascinates audiences the most in the play. It would have been interesting to have seen a young boy like Sharpe originating the role!