Question: Elizabeth Cecil, 16th Baroness de Ros was the daughter of a man that was the son of who?

Context paragraphs:
Una Ross, 26th Baroness de Ros: Una Mary Ross, 26th Baroness de Ros of Helmsley (born "Lady Una Mary Dawson") (5 October 1879 – 9 October 1956) succeeded her mother to the title in 1943.  She was the daughter of Anthony Lucius Dawson, 3rd Earl of Dartrey and Mary Dawson, who held the barony in her own right.

Katherine Villiers, Duchess of Buckingham: Katherine Manners, Duchess of Buckingham, Marchioness of Antrim, 19th Baroness de Ros of Helmsley (died 1649) was the daughter and heir of Francis Manners, 6th Earl of Rutland.  She was known as the richest woman in Britain, apart from royalty.  She married George Villiers, 1st Duke of Buckingham, the favourite, and possibly lover, of King James I of England; and secondly, she married the Irish peer Randal MacDonnell, 1st Marquess of Antrim.

Mary Stewart, Duchess of Richmond: Mary Stewart, Duchess of Richmond and Duchess of Lennox (1622–1685), formerly Lady Mary Villiers, was the daughter of the George Villiers, 1st Duke of Buckingham and Katherine Manners, 19th Baroness de Ros.

Eleanor Beauchamp, Duchess of Somerset: Lady Eleanor Beauchamp, Baroness de Ros and Duchess of Somerset (September 1408 – 6 March 1467) at Wedgenock, Warwickshire, England, was the second daughter of Richard de Beauchamp, 13th Earl of Warwick and Elizabeth de Berkeley, daughter of Thomas de Berkeley, 5th Baron Berkeley.

Henry FitzGerald-de Ros, 22nd Baron de Ros: Henry William FitzGerald-de Ros, 22nd Baron de Ros (12 June 1793 – 28/29 March 1839) was a British nobleman, the son of Lord Henry FitzGerald and his wife Charlotte FitzGerald-de Ros, 21st Baroness de Ros.

Edward Manners, 3rd Earl of Rutland: Edward Manners, 3rd Earl of Rutland, 14th Baron de Ros of Helmsley, KG (12 July 1549 – 14 April 1587) was the son of Henry Manners, 2nd Earl of Rutland, whose titles he inherited in 1563.

Georgiana Maxwell, 27th Baroness de Ros: Georgiana Angela Maxwell, 27th Baroness de Ros of Helmsley ("née Ross") (2 May 1933 – 21 April 1983), succeeded her grandmother Una Ross after the title was called out of abeyance in her favour in 1958.  She was the first woman of her line to be allowed to sit in the House of Lords after the Peerage Act 1963.

Mary Dawson, Countess of Dartrey: Mary Frances Dawson, Countess of Dartrey, 25th Baroness de Ros of Helmsley ("née FitzGerald-de Ros") (31 July 1854 – 4 May 1939) was a British peer.  She was born in London.  Her parents were Dudley FitzGerald-de Ros and Lady Elizabeth Egerton.  Upon her father's death in 1907, Mary succeeded to the title.

Elizabeth Cecil, 16th Baroness de Ros: Lady Elizabeth Manners, 16th Baroness de Ros of Helmsley ("c".  January 1574/1575 – 19 May 1591) was the daughter and heir of Edward Manners, 3rd Earl of Rutland.  On her father's death the Earldom of Rutland devolved upon his brother, the Barony of Ros passed to his daughter, Elizabeth.

William de Ros, 2nd Baron de Ros: William de Ros, 2nd Baron de Ros of Hamlake (c. 1285 – 3 February 1343) was the son of William de Ros, 1st Baron de Ros of Hamlake and Maud de Vaux.

Supporting paragraphs: Elizabeth Cecil, 16th Baroness de Ros Edward Manners, 3rd Earl of Rutland
Answer: Henry Manners