The Libro de Regla of Leire Monastery, compiled in 1076, names "Sancium et Ramirum" as the two sons of "Garsea Sanciones…et uxore sua regina Eximina". "Garsea rex…cum genitrice…Tuta regina et cum filiis Sancio et Ranimiro adque Urraka" donated property to the monastery of San Martín de Albelda by charter dated 953, witnessed by "Sancio rex et Ranimiro rex…". His mother's name is confirmed by the charter dated 29 Jun 971 under which "Endregoto Galindonis et prolem eius Sancio Garsianis rex" donated property. The manuscript of the Codex de Roda entitled "Initium regnum Pampilonam" records that "filius eius Sancius rex" succeeded on the death of "Garsea rex".
He succeeded his father in 970 as SANCHO II García "Abarca" King of Navarre, Conde de Aragón. He inherited a kingdom which had been considerably weakened by Muslim attacks during the last years of his predecessor's rule, and on his accession accepted the suzerainty of Caliph al-Hakam II. King Sancho attempted unsuccessfully to reassert his authority but was defeated in 975 at Estercuel near Tudela. A period of calm followed, presumably due to a pact with al-Mansor confirmed by the latter's marriage with King Sancho's illegitimate daughter. "Endregoto Galindonis et prole eius Sancio Garseanis rex et uxor eius Urraca Fredenandizi" donated property to the monastery of San Pedro de Siresa by charter dated 29 Jun 971. “Sancius rex et Ranemirus rex…cum Clara Urraka regina” donated “la villa de Cirueña” to the “monasterio de San Andrés de Cirueña” by charter dated 13 Nov 972, signed by “Sanctius…rex, cum prolis Garseam” confirmed by “Ranemirus frater ipsius regis…domna Urraka Clara regina”. "Garsias Ferdinandez…cum coniuge mea Ava comitisa" founded the monastery of Infantado de Covarrubias, offering "filiam…nostram Urracam" as a nun there, by charter dated 25 Dec 978, confirmed by "…Sancio rex, Urraka regina, rege Scemeno…". "Sancius rex et Urraka regina…cum germanis nostris Ranimiro et Eximino" confirmed a prior donation to San Pedro de Siresa by "genitor noster Garsea rex" by charter dated 15 Feb 979, confirmed by "Eximino Sancionis, Garsea Furtunionis, Belasco Lihoriz". A charter dated 17 Sep 983 confirmed an agreement between Benedicto Bishop of Nájera and the abbot of Albelda, witnessed by "Sancio rex, Urraca regina, Garsea regulus, Ranimirus regulus, Gondesalvus regulus…". “Sanctio principem...cum coniuge mea Urraca et filios nostros Garsea et Ranemiro una cum Gundesabo” granted “villa in territorio Ataresensem...Badagues” to “domno Santio presbiter Ataresense” by charter dated 1 Jan 985. "Sancio, filio Garseani regis…cum coniux mea Urraka et filios nostros Garsea et Ranimiro et Gundisalvo" confirmed a donation to the monastery of Pampaneto by charter dated 6 May 985. The Muslims renewed their attacks on Navarre from 990, obliging King Sancho to visit Córdoba in 992 to negotiate peace. "Santio Garsseanis rex…cum coniux mea Urraca regina" donated property to the monastery of Leire by charter dated 15 Feb 991. "Sancio rex…cum…subole Urraca regina et vina prole Garsea et coniux eius Eximina et Gundessalvo" donated property to the monastery of San Millán de la Cogolla by charter dated 992, signed by "Sancio rex…Urraca regina, Garsea eorundem filius, Gundessalvus frater eius, Eximina regina, Sancio filius Ranimiri regis, Garsea frater eius, Sancio filius Gogelmi comitis…". 1