Question: When was the third wife to William Herbert, 3rd Earl of Pembroke born? 

Context paragraphs:
William Herbert, 6th Earl of Pembroke: William Herbert, 6th Earl of Pembroke, 3rd Earl of Montgomery (c. 1641 – 8 July 1674) was an English nobleman and politician who succeeded to the titles on 11 December 1669 on the death of his father.

Earl of Ruglen: Earl of Ruglen was a title in the Peerage of Scotland.  Along with the subsidiary titles Viscount of Riccartoun and Lord Hillhouse, it was created on the 14th of April, 1697, for Lord John Douglas-Hamilton, fourth (third surviving) son of William Douglas-Hamilton, Duke of Hamilton, 1st Earl of Selkirk, and his wife Anne Hamilton, 3rd Duchess of Hamilton.  The 1st Earl of Ruglen succeeded as 3rd Earl of Selkirk on the death of his elder brother in 1739.  The Earl's only son William, Lord Daer, died in 1742, so on the death of the Earl of Selkirk and Ruglen in 1744, the Earldom of Selkirk passed to his great-nephew, while the Earldom of Ruglen passed to his daughter, Anne, who had married William Douglas, 2nd Earl of March.  On her death in 1748, the Earldom of Ruglen passed to her only child William, 3rd Earl of March.  He succeeded his first cousin once removed Charles Douglas as 5th Marquess and 4th Duke of Queensberry in 1778.

William Herbert, 3rd Earl of Pembroke: William Herbert, 3rd Earl of Pembroke (8 April 1580 – 10 April 1630) was an English nobleman, politician, and courtier.  He was the son of Henry Herbert, 2nd Earl of Pembroke and his third wife Mary Sidney.  Chancellor of the University of Oxford, he founded Pembroke College, Oxford with King James.  He was warden of the Forest of Dean, and constable of St Briavels from 1608 to 1630.  He served as Lord Chamberlain from 1615 to 1625.  In 1623, the First Folio of William Shakespeare's plays was dedicated to him, together with his brother, Philip Herbert, 1st Earl of Montgomery.

Pembroke College, Oxford: Pembroke College is one of the constituent colleges of the University of Oxford in England, located in Pembroke Square.  The college was founded in 1624 by King James I of England / VI of Scotland, using in part the endowment of merchant Thomas Tesdale, and was named after William Herbert, 3rd Earl of Pembroke, Lord Chamberlain and then-Chancellor of the University.

Pembroke Parish: Pembroke Parish is one of the nine parishes of Bermuda.  It is named after English aristocrat William Herbert, 3rd Earl of Pembroke (1580–1630).

Sonnet 28: Sonnet 28 is one of 154 sonnets written by the English playwright and poet William Shakespeare, it was first published in 1609.  The sonnet is a part of the Fair Youth sequence, in which the poet expresses his love towards a young man — usually referred to as "the young man" or the "friend".  Shakespeare's use of "friend" means more than just of a sexual nature, it highlights the Renaissance ideal of male fidelity and equality.  From sonnets 18 to 126, Shakespeare writes about his relationship with the said young man.  Although the identity of the young man is still unknown, Henry Wriothesley and William Herbert, 3rd Earl of Pembroke, are the two leading contenders.

Mary Sidney: Mary Herbert, Countess of Pembroke (née Sidney; 27 October 1561 – 25 September 1621) was one of the first English women to achieve a major reputation for her poetry and literary patronage.  By the age of 39, she was listed with her brother Philip Sidney, Edmund Spenser, and William Shakespeare, as one of the notable authors of her time in the verse miscellany by John Bodenham, "Belvedere".  The influence of her "Antonius" is widely recognized: it stimulated a revived interest in the soliloquy based on classical models, and was a likely source (among others) for both the 1594 closet drama "Cleopatra" by Samuel Daniel and Shakespeare’s "Antony and Cleopatra" (1607).  Sidney was also known for her translation of Petrarch's "Triumph of Death", but it is her lyric translation of the Psalms that has secured her poetic reputation.

William Herbert, 2nd Earl of Pembroke: William Herbert, 2nd Earl of Pembroke (5 March 1451 – 16 July 1491) was an English nobleman and politician.  He was the son of William Herbert, 1st Earl of Pembroke and Anne Devereux.  His paternal grandparents were William ap Thomas and Gwladys, daughter of Dafydd Gam, and his maternal grandparents were Walter Devereux, Lord Chancellor of Ireland and Elizabeth Merbury.

Earl of Powis: Earl of Powis (Powys) is a title that has been created three times.  The first creation came in the Peerage of England in 1674 in favour of William Herbert, 3rd Baron Powis, a descendant of William Herbert, 1st Earl of Pembroke (c.1501–1570).  In 1687, he was further honoured when he was made Marquess of Powis.  For more information on this creation of the earldom, which became extinct in 1748, see the latter title.

Mary Herbert, Countess of Pembroke (d. 1649): Mary Herbert, Countess of Pembroke (née Mary Talbot) (c. 1594 – March 1649) was the wife of William Herbert, 3rd Earl of Pembroke.

Supporting paragraphs: William Herbert, 3rd Earl of Pembroke Mary Sidney
Answer: 27 October 1561