Derby is one of several individuals who have been claimed by proponents of the Shakespearean authorship question to be the true author of William Shakespeare's works. Derby's candidacy was first proposed in 1891 by the archivist James H. Greenstreet, who identified a pair of letters by the spy George Fenner dating from 1599 in which he reported that Derby was unlikely to advance the Roman Catholic cause, as he was "busy penning plays for the common players." Greenstreet argued that the comic scenes in Love's Labour's Lost were influenced by a pageant of the Nine Worthies only ever performed in Derby's home town of Chester. Greenstreet attempted to develop his ideas in a second paper, but died suddenly in 1892, leaving his arguments incomplete. The theory was revived in The Silent Shakespeare (1915) by the American writer Robert Frazer, who concluded that "William Stanley was William Shakespeare". The idea was then taken up in France and was first advocated in scholarly detail when the Rabelais expert Abel Lefranc published his book, Sous le masque de William Shakespeare: William Stanley, VIe comte de Derby (1918). Several other authors later supported Derby's candidacy, sometimes as part of a group of writers.
While accepting Shakespeare's own authorship of the canon, Leo Daugherty, who wrote an account of Derby's life for the Oxford Dictionary of National Biography, has argued in a recent book that Stanley is the Fair Youth of Shakespeare's sonnets and that Richard Barnfield is the "Rival Poet" Stanley was Barnfield's patron and the subject of his homoerotic sonnet cycle The Affectionate Shepherd, which implied a romantic relationship between the pair.
On 26 January 1595 he married Elizabeth de Vere, daughter of Edward de Vere, 17th Earl of Oxford, and Anne Cecil. Elizabeth's maternal grandparents were William Cecil, 1st Baron Burghley, and his second wife Mildred Cooke. Mildred was the eldest daughter of Anthony Cooke and his wife Anne Fitzwilliam. It has been suggested that the occasion of their wedding was the inspiration for William Shakespeare's Midsummer Night's Dream and that the play was first performed at the couple's wedding festivities. In the early years the relationship was stormy, including claims that Elizabeth had had affairs with Robert Devereux, 2nd Earl of Essex, and Walter Ralegh. The relationship settled down as Derby's financial and social position stabilised. The couple had five children:
1. James Stanley, 7th Earl of Derby (31 January 1607 – 15 October 1651). 2. Robert (d.1632). 3. Anne Stanley, Countess of Ancram (d. 1657). Married first Sir Henry Portman and secondly Robert Carr, 1st Earl of Ancram. 4. Elizabeth Stanley, died young. 5. Elizabeth Stanley. Named after deceased older sister, died young.