Question: Who was the brother of 16th century poet group the Wilton Circle's leader?

full_context: Document 1: Lady Mary Wroth: Lady Mary Wroth (18 October 1587 – 1651/3) was an English poet of the Renaissance. A member of a distinguished literary family, Lady Wroth was among the first female British writers to have achieved an enduring reputation. She is perhaps best known for having written "The Countess of Montgomery's Urania", the first extant prose romance by an English woman, and for "Pamphilia to Amphilanthus", the second known sonnet sequence by an English woman. Wroth's works also include "Love's Victory", a pastoral closet drama.
Document 2: Walter Erle (died 1581): Walter Erle (c.1515/20-1581) ("alias" Erley, Erell, etc.) of Colcombe in the parish of Colyton, of Bindon in the parish of Axmouth, both in Devon, and of Charborough in Dorset, England, was a courtier and servant of the Royal Household to two of the wives of King Henry VIII, namely Catherine Howard (beheaded 1542) and Catherine Parr (survived, died 1548), and successively to his son King Edward VI (1547-1553) and two daughters, Queen Mary I (1553-1558) and Queen Elizabeth I (1558-1603) during their successive reigns. According to Sandon (1983) his popularity as a royal courtier was in part due to his ability as a musician, particularly as a player of the virginal. He is known to have composed at least one work of church music, namely "Ave Vulnus Lateris" ("Hail, O Wound of the Side"), a short votive antiphon in honour of one of the Five Holy Wounds of Jesus, his authorship of which is recorded in Peterhouse College manuscripts 471–474, held in the Cambridge University Library, comprising four partbooks from a set of five copied late in the reign of King Henry VIII, which contain seventy-two pieces of Latin church music. As a courtier-musician he well represents the ideal royal courtier described in "The Courtier" by Baldassare Castiglione (d.1529) and also in "The Boke Named The Governour" by Sir Thomas Elyot (d.1546). Although he was born into a minor gentry family of Devonshire, he founded a dynasty of substantial landed gentry that survives to the present day, his heir (albeit via several female lines) being the Conservative Member of Parliament Richard Grosvenor Plunkett-Ernle-Erle-Drax (born 1958), of Charborough House.
Document 3: Christopher Marlowe: Christopher Marlowe, also known as Kit Marlowe (baptised 26 February 156430 May 1593), was an English playwright, poet and translator of the Elizabethan era. Marlowe was the foremost Elizabethan tragedian of his day. He greatly influenced William Shakespeare, who was born in the same year as Marlowe and who rose to become the pre-eminent Elizabethan playwright after Marlowe's mysterious early death. Marlowe's plays are known for the use of blank verse and their overreaching protagonists.
Document 4: Sonnet 15: Sonnet 15 is one of 154 sonnets written by the English playwright and poet William Shakespeare. It forms a diptych with Sonnet 16, as Sonnet 16 starts with "But...", and is thus fully part of the procreation sonnets, even though it does not contain an encouragement to procreate. The sonnet is within the Fair Youth sequence.
Document 5: Holy Sonnets: The Holy Sonnets—also known as the Divine Meditations or Divine Sonnets—are a series of nineteen poems by the English poet John Donne (1572–1631). The sonnets were first published in 1633—two years after Donne's death. The poems are sonnets and are predominantly in the style and form prescribed by Renaissance Italian poet Petrarch (or Francesco Petrarca) (1304–1374) in which the sonnet consisted of two quatrains (four-line stanzas) and a sestet (a six-line stanza). However, several rhythmic and structural patterns as well as the inclusion of couplets are elements influenced by the sonnet form developed by English poet and playwright William Shakespeare (1564–1616).
Document 6: Melanchthon Circle: The Melanchthon Circle was a 16th-century Lutheran intellectual network centred on the University of Wittenberg in Germany, and its leading theologian Philip Melanchthon. It was identified as significant for its interests in natural philosophy by Lynn Thorndike, in a chapter "The Circle of Melanchthon" in his multi-volume "History of Magic and Experimental Science". Among this circle were found many of the most important early proponents of the heliocentric model of Copernicus. They included Caspar Peucer who became Melanchthon's son-in-law, Erasmus Reinhold, and Georg Joachim Rheticus. Patronage came from Albert, Duke of Prussia.
Document 7: Mary Arundell (courtier): Mary Arundell (died 20 or 21 October 1557), was the only child of Sir John Arundell (1474 – 1545) of Lanherne, Cornwall, by his second wife, Katherine Grenville. She was a gentlewoman at court in the reign of King Henry VIII, serving two of Henry VIII's Queens, and the King's daughter, Princess Mary. She was traditionally believed to have been "the erudite Mary Arundell", the supposed translator of verses now known to have been the work of her stepdaughter, Mary FitzAlan, later the first wife of Thomas Howard, 4th Duke of Norfolk.
Document 8: Pamphilia to Amphilanthus: Pamphilia to Amphilanthus is a sonnet sequence by the English Renaissance poet Lady Mary Wroth, first published as part of "The Countess of Montgomery's Urania" in 1621, but subsequently published separately. It is the second known sonnet sequence by a woman writer in England (the first was by Anne Locke). The poems are strongly influenced by the sonnet sequence "Astrophel and Stella" (1580) penned by her uncle Sir Philip Sidney. Like Sidney's sequence, Wroth's sonnets passed among her friends and acquaintances in manuscript form before they were published in 1621. In Wroth's sequence, she upends Petrarchan tropes by making the unattainable object of love male.
Document 9: 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.
Document 10: Wilton Circle: The Wilton Circle were an influential group of 16th-century English poets, led by Mary Sidney. They were based at Wilton House, Wiltshire, which was run by the half-brother of Walter Raleigh. Sidney turned Wilton into a "paradise for poets", and the circle included Edmund Spenser, Michael Drayton, Sir John Davies and Samuel Daniel.
Document 11: Englands Helicon: Englands Helicon is an anthology of Elizabethan pastoral poems compiled by John Flasket, and first published in 1600. There was an enlarged edition in 1614. The poets involved cannot all be identified, since there are a number of poems marked as 'anonymous': they do include Edmund Bolton, William Byrd, Henry Chettle, Michael Drayton, Robert Greene, Christopher Marlowe, Anthony Munday, George Peele, Walter Raleigh, Henry Constable, William Shakespeare, Philip Sidney, Edmund Spenser, John Wootton, William Smith. The most celebrated poem is Marlowe's 'Come live with me and be my love'. This and several other lyrics have musical settings extant, in this case by William Corkine.
Document 12: Philip Herbert, 4th Earl of Pembroke: Philip Herbert, 4th Earl of Pembroke and 1st Earl of Montgomery (10 October 1584 – 23 January 1650) was an English courtier, nobleman, and politician active during the reigns of James I and Charles I. Philip and his older brother William were the 'incomparable pair of brethren' to whom the First Folio of Shakespeare's collected works was dedicated in 1623.
Document 13: Astrophel and Stella: Probably composed in the 1580s, Philip Sidney's Astrophil and Stella is an English sonnet sequence containing 108 sonnets and 11 songs. The name derives from the two Greek words, 'aster' (star) and 'phil' (lover), and the Latin word 'stella' meaning star. Thus Astrophil is the star lover, and Stella is his star. Sidney partly nativized the key features of his Italian model Petrarch, including an ongoing but partly obscure narrative, the philosophical trappings of the poet in relation to love and desire, and musings on the art of poetic creation. Sidney also adopts the Petrarchan rhyme scheme, though he uses it with such freedom that fifteen variants are employed.
Document 14: Mary Robinson (poet): Mary Robinson (née Darby; 27 November 1757? – 26 December 1800) was an English actress, poet, dramatist, novelist, and celebrity figure. During her lifetime she was known as "the English Sappho". She earned her nickname "Perdita" for her role as Perdita (heroine of Shakespeare's "The Winter's Tale") in 1779. She was the first public mistress of King George IV while he was still Prince of Wales.
Document 15: Thomas Walsingham (literary patron): Sir Thomas Walsingham (c. 1561 – 11 August 1630) was a courtier to Queen Elizabeth I and literary patron to such poets as Thomas Watson, Thomas Nashe, George Chapman and Christopher Marlowe. He was related to Elizabeth's spymaster Francis Walsingham and the employer of Marlowe's murderer Ingram Frizer. This connection is one of the reasons offered for suggesting that Marlowe's death may have been linked with intelligence work, and not a dispute over a bill for food and accommodation, as in the coroner's verdict.
ground_truth: Philip Sidney