Her parentage is erroneously given by many secondary sources. She is known to have been a sister of Juhel de Mayenne, but the generation is not clear. Cawley and van de Pas both identify Clémence de Mayenne as the daughter of Geoffroi II, seigneur of Mayenne (died 1169), by his 2nd wife, Isabel of Meulen. Douglas Richardson has shown the impossibility of this filiation, and demonstrated that she must have been a daughter of child of Geoffroi II's 1st wife, Constance of Brittany. (Douglas Richard, soc.genealogy.medieval, Feb. 13, 2012.) -------------------- [from Medlands]

   CLEMENCE de Mayenne (-before 1209). Her parentage is confirmed by the undated charter by which her uterine half-brother "Mauritius dominus Credoni" confirmed the donation by "Constantia soror mea" of revenue set by "dominus Juhellus frater meus" at "apud Harperiam" to the abbey of Clarei, by undated charter, witnessed by "…domina Isabel matre mea, domina Gervasia…"[734]. Her parentage is confirmed by the the charter dated 1205 under which her daughter "Margarita domina Sabolii" confirmed donations to Fontaine-Daniel by "avunculi mei domini Juhelli de Meduana"[735]. Dame d'Angon.
   m ROBERT [IV] Sire de Sablé, son of ROBERT [III] Sire de Sablé [Nevers] & his wife Hersende --- (-in Palestine [1195]).

   [734] Guyard de la Fosse (1850), Preuves, XVII.

   [735] Fontaine-Daniel, XIX, p. 36.