The parentage of Sancho is unclear from the primary sources. Although the patronymic of his son Garcia indicates his father's name, Settipani states that there is no proof that Sancho was related to the previous dukes of Gascony... However, a clue is provided by the undated charter, under which Sancho’s great-grandson "dominus Willelmus Sancii comes Gasconiorum" donated property to the abbey of Saint-Vincent-de-Lucq. The document records that "quomodo venisset de Hispania avus domni Willelmi ubi se contulerat pater eius tempore domni Ludovici imperatoris" ("the grandfather of seigneur Guillaume had come from Spain where his father had taken refuge at the time of emperor Louis"). The "avus domni Willelmi" was Count Garcia [I] Sanchez, so the latter's own father would have been Sancho. The document also states that the consanguinity of Guillaume Sancho with Gaston Centule Vicomte de Béarn was proved: "quidem Rex" (which from the context appears to refer to Sancho) invested "avo Vicecomitis [Gasto Centuli Vicecomes Bearnensis], qui erat de eius progenie" with "hac patria". This statement provides a strong suggestion that Sancho and his son were related to the previous dukes of Gascony, from whom the vicomtes de Béarn were probably descended although the documentation which proves this relationship has not survived. Another perspective is provided by the Genealogica Comitum Guasconiæ which records that "maxima pars nobilium virorum Guasconiæ" left for "Hispaniam ad Consulem Castellæ" (presumably during the time of Emperor Louis I, although this is not stated in the document), that "Sancius Mitarra, minimus filiorum eius" returned to Gascony, where he was made "Consul" and had a son "Mitarra-Sancius" who was father of "Garsiam-Sancium Curvum". The distinction between the two persons "Sancius Mitarra" and "Mitarra Sancius" appears unlikely from a chronological point of view, especially given the patronymic assigned to Comte Garcia [I] in other sources... Sancho’s birth date is estimated from the estimated birth date of his son. The charter of Saint-Vincent-de-Lucq, quoted above, suggests that Sancho must have been invested as Duke of Gascony in the latter half of the 9th century, maybe in 864 after the death of Duke Arnaud. The document refers to him as "Rex". It is unclear why he should have been accorded this title. However, as noted below, the same title is referred to in a charter dated to [920] in which his son calls himself "Garsias Sanctii consul filius regis Sancii". This document presumably provided the basis on which Monlezun states that Sancho was the third son of "Garsias-Ximenes" king of Pamplona, and that he eventually succeeded as king of Navarre after 901, although he cites no primary sources. It appears improbable from a chronological point of view that Sancho could have been the same person as Sancho I García King of Navarre, whose succession in Navarre is dated to 905 and death to 925. The surprising conclusion appears to be that Sancho, father of Garcia [I], was referred to in contemporary documentation as "king" by way of honorific title. 1
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