“…Ranimirus…regulus, Gundesalbo regulus…Sancio regulus…” confirmed the charter dated 31 Dec  under which “Garsea Sancioni rex…cum coniux mea Eximina” donated property to the monastery of Leire. The Historia Silense records that "Sancius filius eius" succeeded on the death of King García.
He succeeded his father in 999 as SANCHO III "el Mayor" King of Navarre, Conde de Aragón, under the regency of --- until 1005. The Muslim attacks against Navarre continued unabated, culminating in the capture of Pamplona in 1000. “Sancius…rex…cum coniuge mea regina domina Maiora” donated property to the monastery of Leire by charter dated 17 Apr 1014. "Sancius rex…cum coniuge mea Mumadonna regina" donated property to the monastery of San Millán de la Cogolla by charter dated 24 Jun 1014, signed by "…sennor Lope Sancii maiordomus, sennor Lope Ennecones botilarius, sennor Garsea Lopez, sennor Enneco Sanchiz Naialensis, sennor Fortun Sanchiz frater eius, sennor Eximino Garceiz Osselensis, sennor Fortun Belasquiz Funensis".
Conde de Ribagorza : the end 13th century “Crònica d´Alaó Renovada” records that, after the death of “Guillelmum Ysarni, quem genuerat Ysarnus prefatus ex concubina” (dated to 1018]), Ribagorza was inherited by “rex Sancius...jure propinquitatis”, explained because “Major comitissa soror comitis Sancii de Castella” married “comitis Paliarensis Raimundi Suniarii” and remained in Ribagorza after their marriage was ended “consanguinitatis causa”, and because “rex Sancius Pampilonensis” married “filiam predicti comitis Sancii de Castella...Majorem”. "Sancius rex" confirmed a donation of property to the monastery of San Millán de la Cogolla by his parents by charter dated 1020, signed by "Momadonna regina, Garsea regulus, Ranimirus regulus prolis regis...Lope Sanchiz maiordomus, Lope Ennecones botellarius, sennor Enneco Sancii Naialensis et Muensis, sennor Fortun Belasquiz Funensis". King Sancho III confirmed the donation of the monastery of San Cristóbal de Tobia to San Millán de la Cogolla by charter dated 1020, signed by "Momadonna regina cum filiis meis Garsea regulus, Ranimirus frater eius, Ranimirus alius frater eius...". "Sancius rex et uxor mea Muma dompna regina" donated property to the monastery of Yarte y Anoz by charter dated 17 May 1024, confirmed by "Garsias regulus, Ranimirus frater eius, Gunçalvus frater eius, Fredinandus frater horum…". He claimed the county of Castile in his wife's name after the murder of her brother conde García Sánchez in 1029, and incorporated the whole of Castile into his kingdom. Taking advantage of the weakness of the caliphate which followed the death of Abd al-Malik, Sancho III led a rapid of expansion of the territory of Navarre to the west, capturing most of the kingdom of León. He forced the marriage of his son Fernando to Sancha de León, sister of Vermudo III King of León. He captured the city of León from Vermudo in 1034 when he declared himself emperor of all the Hispano-Christian principalities. Strongly influenced by French monarchist theories and feudal norms, he was the first monarch to adopt the French practice of claiming to rule "by the grace of God", later adopted by the other Iberian monarchies, and introduced the term vassal into local usage.
His personal empire was short-lived as he decreed the division of his territories between his sons after his death. The Chronicon Burgense records the death in 1035 of “Sancius Rex Abarca”. The manuscript of the Codex de Roda entitled "Initium regnum Pampilonam" records the death in 1035 of "Sancius rex" and his burial "Onie monasterio", although the passage is garbled as the earlier part of the sentence records the succession in 970 of King Sancho II. 1