 Alfonso VI's son and heir, Sancho Alfónsez, is known in one interpolated and therefore inaccurate charter, dated 12 January 1102, as "Sancho son of the emperor" ("Sancius filius Imperator").There is some controversy over Alfonso's use of the title "Emperor of the Two Religions" ("al-Imbraţūr dhī-l-Millatayn"), which appears in a surviving letter he sent to King al-Mu‘tamid ibn Abbād of Seville.The two letters exchanged between the two kings in 1085 are preserved only in Arabic in the text of the fourteenth-century chronicle "Al-Ḥulal al-Mawšiyya fi Ḍikr al-Ajbār al-Marrākušiyya".