Mathilde de Brienne-Eu

-http://fmg.ac/Projects/MedLands/normacre.htm#MathildeBrienneEuMAlfo...

c) [MATHILDE ([1272/74]-[1348/53]). The Nobiliario of Pedro Conde de Barcelos records that "D. Alonso Guedella" married "D. Mafalda"[1610]. Salazar y Castro asserts that she was "Mathilde de Narbonne señora de Lunel, daughter of Aimeric [VI] Vicomte de Narbonne and his wife Sibylle de Foix[1611]. This is presumably based on Zurita’s Anales de la Corona de Aragón, written [1562/80], which record that "don Alonso hijo del Infante don Fernando" married "en Francia…Mofalda…quanto yo congeturo fue de la casa de los Vizcondes de Narbona, y con ella huvo el señorio de Lunel"[1612]. Masnata relates that the seigneurie de Lunel passed to the French crown on the death in 1295 of Rousselin last seigneur de Lunel, concluding therefore that Alfonso de la Cerda could not have inherited the seigneurie through his wife (it was granted by Charles IV King of France to Alfonso’s son, Alfonso, see below)[1613]. Masnata found no basis for the supposed origin of Mathilde in Narbonne, and suggests that the wife of Alfonso de la Cerda was Mathilde, daughter of Jean de Brienne Comte d'Eu. He reaches this conclusion by process of elimination of other possible candidates connected with the French royal family, and after remarking that Jean de Brienne is reported, in early secondary sources, to have had a daughter named Mathilde whose marriage is not otherwise recorded[1614]. Masnata comments that the chronology is correct and the onomastics favourable, as the name Juan passed into the Cerda family after this marriage[1615]. He also quotes the Continuator of the Chronique de Jean de Saint-Victor which names "filz au roy d’Espagne et…une dame de Normandie" as the parents of "monseigneur Aufour" (which refers to Alphonse de la Cerda, son of Alfonso and his wife Mathilde)[1616]. It should nevertheless be emphasised that Masnata has not identified a primary source which confirms that his hypothesis is correct. She was Alfonso's mistress from [1288/89].

m (1290) don ALFONSO de la Cerda de Castilla, son of Infante don FERNANDO "él de la Cerda" de Castilla y León & his wife Blanche de France (Valladolid 1270-Piedrahita shortly after 23 Dec 1324).]

https://www.familysearch.org/tree/person/details/GD27-W4N

Mathilde de Brienne-Eu is daughter of Jean de Brienne, Comte d'Eu and Beatrice de Châtillon, wife of Alfonso 'el Desheredado' de la Cerda.

http://www.fundacionmedinaceli.org/casaducal/fichaindividuo.aspx?id=11