According to Charles Cawley, in his FMG Medieval Lands database, and based upon primary sources, it is highly unlikely that Ermengarde de Gévaudan, the daughter of Etienne de Brioude de Gevaudan and the oft-married Adelais d'Anjou, was married to Robert I d'Auvergne as is often believed. Cawley presents the scenario that Ermengarde may in fact have been the same as Humberge, who was married instead to Robert d'Auvergne's father Guillaume IV d'Auvergne

However, Cawley also does not address another theory, that Ermengarde de Gevaudan married Richard I de Millau, since RIchard's son Richard II somehow became VIcomte of Gevaudan. This needs to be explored.

From Cawley:

[HUMBERGE [Ermengarde] ([970/75]-).

• "Umberga" donated property to Sauxillanges for the souls of "senioris mei Vuillelmi et…filiorum meorum tam vivis quam etiam defunctis" by charter dated to [1000/10][1238].
• "Domni Stephani episcopi, domni Rotberti, domni Vuillelmi, Umbergane comitisse matris eorum" signed a charter dated to [1013/21] under which property was donated to Sauxillanges[1239].
• There is doubt about Humberge's parentage but the hypothesis shown here appears to provide the best solution to various chronological difficulties.
• The Flandria Generosa names "Ermengardis comitissa Arvenensis" as sister of "Constantia regina Francorum", when outlining the basis for the consanguinity between their great-great-grandchildren, Baudouin VII Count of Flanders and [Hawise] de Bretagne, which provided the grounds for the couple's separation[1240]. It has been assumed in many secondary sources[1241] that this passage means that "Ermengarde" was the full sister of Queen Constance (who was the third wife of Robert II King of France) and therefore that she was the daughter of Guillaume [II] Comte de Provence by his second marriage to Adelais d'Anjou. However, this is chronologically impossible.
• The marriage of "Ermengarde's" daughter, also named Ermengarde, to Eudes II Comte de Blois, is dated to 1005 according to the Chronicle of Alberic de Trois Fontaines[1242]. Even if this date is inaccurate, the estimated birth date of Ermengarde junior's eldest son is [1010], and the marriage of her daughter is dated to 1018 (although the chronology suggests that this may have been an infant betrothal or marriage).
• Assuming that there is a degree of accuracy in these three dates, the daughter of "Ermengarde" Ctss d'Auvergne could not have been born later than [995] at the latest. This places the birth of "Ermengarde" senior to [980] at the very latest, about five years before Adelais's marriage to Guillaume Comte de Provence. Given that Adelais's third marriage to Louis V King of the West Franks was childless, and her second marriage to Raymond IV Comte de Toulouse was brief, it is therefore most likely that "Ermengarde" was Adelais's daughter by her first marriage to Etienne de Brioude.
• Some corroboration for this hypothesis is found in the charter dated 1011 under which "Poncius comes Gabalitanensis" (who was the son of Adelais d'Anjou by her marriage to Etienne de Brioude) donated property to Saint-Julien de Brioude, for the souls of "genitorum suorum Stephani et Alais et uxoris eius Theotbergæ et filiorum eius Stephani et Poncii vel fratrum eius Bertrandi et Willelmus et nepotum eius Stephani, Rotberti et Willelmi", by charter dated Feb [1010], signed by "Roberti vicecomitis, Willelmi fratris eius…"[1243]. In this scenario, Etienne, Robert and Guillaume would be the sons of Pons's full sister "Ermengarde" Ctss d'Auvergne. However, this raises yet more difficulties.
• The secondary sources also assume that "Ermengarde's" husband was Robert [I] Comte d'Auvergne. However, the only known son of Comte Robert [I] was Guillaume [V] Comte d'Auvergne. Assuming that the "nepotes" of Comte Pons are named in order of seniority in the 1011 charter, "Vuillelmi" would have been the youngest brother. No other reference has been to found to his assumed older brothers Etienne and Robert.
• In any case, it is unlikely that Guillaume [V] Comte d'Auvergne would have been born much before [995/1000] for consistency with the dates of his marriage and his death. If this is correct, it would raise doubts about the use of the title "vicecomes" in the 1011 charter, as their father would still have been at the height of his power.
• All these difficulties would be solved if the "nepotes" of Comte Pons were in fact the three known sons of Guillaume [IV] Comte d'Auvergne, not of Robert [I] Comte d'Auvergne. If this is correct, "Ermengarde" would in fact have been "Humberge", who, as shown above, is named in other primary sources as the wife of Comte Guillaume.

m GUILLAUME [IV] Comte d'Auvergne, son of [GUY Comte d'Auvergne & his wife Ausenda ---] (-[1016]).