Person:Constance De Powys (1)

Ormerod, George; William Smith; William Webb; and Peter Leycester. The history of the county palatine and city of Chester: compiled from original evidences in public offices, the Harleian and Cottonian mss., parochial registers, private muniments, unpublished ms. collections of successive Cheshire antiquaries, and a personal survey of every township in the county, incorporated with a republication of King's Vale royal and Leycester's Cheshire antiquities. (London: Lackington, Hughes, Mavor & Jones, 1819 (London : Nichols, Son, and Bentley))
2:333.

"David the Bastard, alias le Clerc [son of William de Malpas by Beatrix de Montalt], intruder into his father's moiety of Malpas" married "Constance, daughter of Owain Kevelioe, prince of Powys."

Another compiler indicates that Constance was the granddaughter of Owain Cyfeiliog (assumed to be the same as Kevelioe) rather than his daughter. The dates fit better for this (Owain died 1197 and Gwenwynwyn died 1216).
↑ Birth year estimated based on assuming that she was granddaughter of Owain Cyfeiliog rather than his daughter. Birth year estimated as late as possible for being Gwenwynwyn's daughter (he died in 1216), to fit into the estimated dates for the family into which she married.