Hawise, daughter of Geoffrey Fitz Piers, Earl of Essex, by his (2) wife, Aveline de Clare (Hawise received as her maritagium the manor of Streatley, Berkshire from her half-brother, William de Mandeville, Earl of Essex). [Ancestral Roots]
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He married, 1stly, Hawise (h). [Complete Peerage IX:20, XIV:478, (transcribed by Dave Utzinger)]
(h) She was apparently daughter of Geoffrey FitzPiers, Earl of Essex. The author of "Dunster" suggested that she was daughter, and possibly heir, of William Fleming, but after examination of documents cited in the account of Streatley given in VCH, Berkshire, he now inclines to credit the older view as above. A deed executed by her as Domina Hawise de Mohun is copied in the Pole MS.