Abouthistory
4. Cecilia (or Cecily) (c. 1056 – 1126), Abbess of Holy Trinity, Caen.
William Conqueror is known to have had nine children, though Agatha, a tenth daughter who died a virgin, appears in some sources. Several other unnamed daughters are also mentioned as being betrothed to notable figures of that time. Despite rumours to the contrary (such as claims that William Peverel was a bastard of William)[20] there is no evidence that he had any illegitimate children.
http://en.wikipedia.org/wiki/Cecilia_of_Normandy
The book, 'Kings & Queens of Great Britain'
Cecilia of Normandy (or Cecily; c.1056 – 30 July 1126) possibly the eldest daughter of William the Conqueror and Matilda of Flanders. Her brothers were Kings William II of England and Henry I of England. She was buried within the walls of the Abbey of Sainte-Trinité at Caen. Her tomb is walled up without any opening being left through which it can be discovered.
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