 Pelagius of Oviedo wrote that Alfonso was 79 when he died, but that would place his birth around 1030, before his parents' marriage.According to the "Historia silense", the eldest child of Ferdinand I and Sancha, a daughter called Urraca, was born when her parents were still Count and Countess of Castile, so her birth could be placed in 1033–34.The second child and eldest son, Sancho, must have been born in the second half of 1038 or in 1039.