Question: Who is Robert Sidney, 1St Earl Of Leicester's paternal grandfather?

Knowledge 1: Robert Sidney, 1st Earl of Leicester
Robert Sidney, 1st Earl of Leicester (19 November 1563 – 13 July 1626), second son of Sir Henry Sidney, was a statesman of Elizabethan and Jacobean England.He was also a patron of the arts and an interesting poet.His mother, Mary Sidney "née" Dudley, was a lady-in-waiting to Queen Elizabeth I and a sister of Robert Dudley, 1st Earl of Leicester, an advisor and favourite of the Queen. [SEP] Knowledge 2: Henry Sidney
Sir Henry Sidney (1529 – 5 May 1586), Lord Deputy of Ireland, was the eldest son of Sir William Sidney of Penshurst, a prominent politician and courtier during the reigns of Henry VIII and Edward VI, from both of whom he received extensive grants of land, including the manor of Penshurst in Kent, which became the principal residence of the family.Henry Sidney was brought up at court as the companion of Prince Edward, afterwards King Edward VI, and he continued to enjoy the favour of the Crown, serving under Mary I of England and then particularly throughout the reign of Queen Elizabeth I.He was instrumental in the Elizabethan conquest of Ireland, serving as Lord Deputy three times.His career was controversial both at home and in Ireland.
Knowledge 1: Robert Sidney, 1st Earl of Leicester
Robert Sidney, 1st Earl of Leicester (19 November 1563 – 13 July 1626), second son of Sir Henry Sidney, was a statesman of Elizabethan and Jacobean England.He was also a patron of the arts and an interesting poet.His mother, Mary Sidney "née" Dudley, was a lady-in-waiting to Queen Elizabeth I and a sister of Robert Dudley, 1st Earl of Leicester, an advisor and favourite of the Queen. [SEP] Knowledge 2: Robert Sidney, 2nd Earl of Leicester
Robert Sidney, 2nd Earl of Leicester (1 December 1595 – 2 November 1677) was an English diplomat and politician who sat in the House of Commons between 1614 and 1625 and then succeeded to the peerage as Earl of Leicester.
Knowledge 1: Robert Sidney, 1st Earl of Leicester
Robert Sidney, 1st Earl of Leicester (19 November 1563 – 13 July 1626), second son of Sir Henry Sidney, was a statesman of Elizabethan and Jacobean England.He was also a patron of the arts and an interesting poet.His mother, Mary Sidney "née" Dudley, was a lady-in-waiting to Queen Elizabeth I and a sister of Robert Dudley, 1st Earl of Leicester, an advisor and favourite of the Queen. [SEP] Knowledge 2: Philip Smythe, 2nd Viscount Strangford
Philip Smythe, 2nd Viscount Strangford (23 March 1634 – 8 August 1708) was an English politician who sat in the House of Commons in 1660.Smythe was the son of Thomas Smythe, 1st Viscount Strangford of Westenhanger and Sturry, Kent and his wife Lady Barbara Sidney, the daughter of Robert Sidney, 1st Earl of Leicester.He inherited the title on the death of his father in 1635.In 1659 he was arrested at Canterbury, with his half brother Thomas Colepeper, following the uprising, and was released on parole and bail for £5,000.In 1660, Smythe was elected Member of Parliament for Hythe in the Convention Parliament.Smythe died at the age of 74.Smythe married firstly his cousin Isabella Sidney, daughter of Robert Sidney, 2nd Earl of Leicester.After her death in 1663, he married Mary, daughter of George Porter.He was succeeded by his son Endymion.

Answer: Sir William Sidney