a short summary from Wikipedia:

Lady Cecily Neville

Duchess of York

Spouse: Richard Plantagenet, 3rd Duke of York

Issue: Anne of York, Duchess of Exeter

Edward IV, King of England

Edmund, Earl of Rutland

Elizabeth of York, Duchess of Suffolk

Margaret, Duchess of Burgundy

George Plantagenet, 1st Duke of Clarence

Richard III, King of England

House: House of York

House of Neville

Father: Ralph Neville, 1st Earl of Westmorland

Mother: Joan Beaufort

Born: 3 May 1415

Raby Castle, Durham

Died: 31 May 1495 (aged 80)

Berkhamsted Castle, Hertfordshire

Burial: St Mary and All Saints Church, Fotheringhay

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"Cecily Neville, Duchess of York (3 May 1415 – 31 May 1495) was the wife of Richard Plantagenet, 3rd Duke of York, and the mother of two Kings of England, Edward IV and Richard III. Lady Cecily Neville was a daughter of Ralph Neville, 1st Earl of Westmorland, and Joan Beaufort, Countess of Westmorland. Her maternal grandparents were John of Gaunt, 1st Duke of Lancaster, and Katherine Swynford. John of Gaunt was the third surviving son of Edward III of England and Philippa of Hainault.

She was the aunt of Richard Neville, 16th Earl of Warwick, one of the leading peers and military commanders of his generation, and also the great-great-great-aunt of the queen consort Catherine Parr, sixth wife of her great-grandson, King Henry VIII.

Cecily was called "the Rose of Raby", because she was born at Raby Castle in Durham, and "Proud Cis", because of her pride and a temper that went with it. Historically she is also known for her piety. She herself signed her name "Cecylle"."

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Wikipedia links:

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other links:

http://www.findagrave.com/cgi-bin/fg.cgi?page=gr&GRid=69066818

http://www.geneall.net/U/per_page.php?id=1705

http://www.genealogy4u.com/genealogy/getperson.php?personID=I310&tree=western2007

http://histfam.familysearch.org/getperson.php?personID=I5289&tree=Nixon

http://parsonsfamily.blogware.com/indiI3319.html

http://www.royalist.info/execute/biog?person=67

http://www.thepeerage.com/p10164.htm#i101633

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Citations:

[S6] G.E. Cokayne; with Vicary Gibbs, H.A. Doubleday, Geoffrey H. White, Duncan Warrand and Lord Howard de Walden, editors, The Complete Peerage of England, Scotland, Ireland, Great Britain and the United Kingdom, Extant, Extinct or Dormant, new ed., 13 volumes in 14 (1910-1959; reprint in 6 volumes, Gloucester, U.K.: Alan Sutton Publishing, 2000), volume XII/2, page 908. Hereinafter cited as The Complete Peerage.

[S8] Charles Mosley, editor, Burke's Peerage and Baronetage, 106th edition, 2 volumes (Crans, Switzerland: Burke's Peerage (Genealogical Books) Ltd, 1999), volume 1, page 17. Hereinafter cited as Burke's Peerage and Baronetage, 106th edition.

[S11] Alison Weir, Britain's Royal Family: A Complete Genealogy (London, U.K.: The Bodley Head, 1999), page 134. Hereinafter cited as Britain's Royal Family.

[S11] Alison Weir, Britain's Royal Family, page 132.

[S6] Cokayne, and others, The Complete Peerage, volume XII/2, page 909.

[S6] Cokayne, and others, The Complete Peerage, volume III, page 260.