When was the third wife to William Herbert, 3rd Earl of Pembroke born? 
William Herbert, 3rd Earl of Pembroke:  He was the son of Henry Herbert, 2nd Earl of Pembroke and his third wife Mary Sidney. 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.
27 October 1561