Notes under Reginald de Peyton son of Walter:
The first of the family on record by the name of Peyton was Reginald de Peyton, second son of Walter, Lord of Sibton, younger brother of Mallet, sheriff of Yorkshire. This Reginald held the lordships of Peyton Hall, in Ramshold, and Boxford, in Suffolk, of Hugh de Bigod; he was stewerd to Roger Bigod, Earl of Norfolk, and gave lands to the monks of Thetford, to pray for the soul of Hugh Bigod. He had two sons, William, who held certain lands in Boxford, of the fee of the abbey of St. Edmundsbury, as appears by charter of his nephew John, and John de Peyton. [John Burke & John Bernard Burke, Extinct and Dormant Baronetcies of England, Ireland, and Scotland, Second Edition, Scott, Webster, & Geary, London, 1841, p. 408, Peyton, of Isleham]
The Domesday book states that Walter de Caen was Lord of Sibton, given to him by Robert Malet's mother (William Malet's widow).
The giving of Sibton to Walter de Caen by William Malet's widow implies some relationship, possibly brother (but most likeley bastard son--see below). See Domesday Book for history of Sibton.
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The following quotation from the "Butler Family History" indicates that Walter is son of William Malet, which would explain the age difference between Walter & William (ie. they weren't brothers as indicated above.}:
Theobald Blake Butler, a leading authority on the history of the family, who died only this year [1965] and whose works are now available to scholars in the National Library, Dublin, the British Museum and the Irish Genealogical Research Society, laboriously traced back to Domesday the lands which this family subsequently held in East Anglia and Lancashire and discovered that at least nine of the sixteen or more holdings which our Hervey was believed to have owned in Norfolk and Suffolk were entered in Domesday Book under the ownership of Walter de Caen. The discovery led him to surmise that the paternal ancestor of the Butlers was Walter de Caen (son of William Malet who accompanied the Conqueror and, being half Saxon, was entrusted with the burial of King Harold after the Battle of Hastings).
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Based on the "Butler Family History" and the approximate birth dates, I am making Walter de Caen son of William Malet. I think, however, that the name implies an illegitmate birth, so he may not be the son of Walter's wife, even though her giving him Sibton would imply blood relationship. Perhap he was son of her, but not William Malet?