Wikipedia
Blanca of Navarre (Basque: Blanka Garzeitz, Spanish: Blanca Garcés; aft. 1133, Laguardia, Álava – August 12, 1156) was Queen of Castile, the daughter of King García Ramírez of Navarre and his first wife Margaret of L'Aigle. Blanca married Sancho III of Castile, regent of Castile (subject to his father Alfonso VII) on February 4, 1151 in Carrión de los Condes, Palencia, after travelling from Calahorra, Logroño, in January[2]. The marriage was arranged to insure closer ties between León-Castile and Navarre.[3] As was traditional, Blanca confirmed documents with her husband, so her activity may be traced until 1155.

On November 11, 1155 she gave birth to the future king Alfonso VIII. There appears to be no record of her activities after December 1155, and she died on August 12, 1156. The cause of her death seems to have been complications of a new pregnancy, a child named García.[4] In addition, she had other children buried in the church of San Pedro in Soria, although they are not identified. That her death was caused by a pregnancy is recorded in an epitaph engraved on her tomb, however, the engraving did not survive a sixteenth-century reconstruction of the royal tombs in Nájera. Her sarcophagus lid was preserved, and it represents the queen's deathbed with members of the court, including her husband, mourning her passing.[5] Blanca was buried in the pantheon of the Navarrese kings in the monastery called Santa María la Real of Nájera, to which Sancho made donations on her behalf. The sarcophagus of the queen is regarded as a primary example of the ability to express human emotions in visual images in the 12th century.
Regerences:
1. Gonzalez, Julio (1960). El reino de Castilla en la epoca de Alfonso VIII, vol. 1. Madrid: CSIC Escuela de Estudios Medievales. p. 145, note 37.
2. Serrano, Luciano (1935). El Obispado de Burgos y Castilla, primitiva desde el siglo V al XIII, vol. 2. Madrid: Instituto de Valencia de Don Juan. p. 43, note 4. Retrieved 24 February 2018.
3. Reilly, Bernard F. (1998), The Kingdom of León-Castilla under King Alfonso VIII (1126-1157), Philadelphia, University of Pennsylvania Press, p. 112.
4. Porreño, Baltasar. "Historia del Santo Rey Alonso el bueno y noble, noveno de este nombre entre los Reyes de Castilla y León, Mss/778 (nineteenth-century copy), fol. 3r,". Biblioteca Digital Hispánica. Biblioteca Nacional de España. Retrieved 16 November 2017.
5. Valdez del Alamo, Elizabeth (1996). "Lament for a Lost Queen: The Sarcophagus of Doña Blanca in Nájera". Art Bulletin. 78 (2): 311.


Blanca and Sancho had two named sons:

Alfonso VIII of Castile
Infante García, who died at birth in 1156, apparently also resulting in the death of Blanca.