MATILDA (-after 1128). Guillaume de Jumièges names Mathilde as illegitimate daughter of King Henry I and her husband "Conan comte de la Petite-Bretagne"[234]. Her marriage is referred to by Orderic Vitalis[235], in a later passage recording that the betrothal occurred before the alliance was agreed between Henry I King of England and Louis VI King of France, which is dated to 1113[236]. "Alanus, Hoelli filius, comes totius Britannie et princeps" donated property to the abbey of Redon with the consent of "suorum filiorum Conani et Gaufridi, necnon et uxoris suæ Hermengardis et uxoris filii sui Conani, Mahalt" by charter dated 1112[237]. "Mathilda comitissa et Haduisa soror comitis Conani" signed the undated charter Duke Conan III donated a fishery to the abbey of Mont-Saint-Michel[238]. "Ermengardis mater mea et uxor mea Matildis…" signed the charter dated 1128 under which Duke Conan III confirmed the possessions of the monks of Saint-Melaine de Rennes[239]. m (1112 or before) CONAN III "le Gros" Duke of Brittany, son of ALAIN IV "Fergant" Duke of Brittany & his second wife Ermengarde d'Anjou (-17 Sep 1148).
http://fmg.ac/Projects/MedLands/BRITTANY.htm#_Toc284059584