The Chronicon Regum Legionensium names "Alfonso and Teresa" as the children of King Vermudo and his wife Elvira. The charter dated 4 Oct 1032, under which [his son] King Vermudo III exchanged “villa Lapeto qui fuit de abia mea regina domna Velasquita” with “comes Pelagio Froilaz et uxor vestra comitissa Ildontia Ordoniz” for “villa...Framilani que fuit de Monnio Didaz...in territorio Asma prope domo Sancto Iuliano”, indicates that Velasquita was the mother of King Alfonso V but this is contradicted by the Chronicon Regum Legionensium quoted above. The chronology appears unfavorable for King Alfonso to have been born from King Vermudo´s marriage to Velasquita. Presumably “abia” is used loosely in the charter dated 4 Oct 1032 which is quoted above. He was "three years of age" when his father died, according to the Historia Silense, five years old according to the Chronicon Regum Legionensium. The Crónica de Sampiro, as reproduced in the Historia Silense, records that "Adefonsus filius eius…annos tres" succeeded on the death of King Vermudo II.
He succeeded his father in 999 as ALFONSO V King of León. Ibn-Khaldun states that Alfonso V King of León succeeded under the regency of "le comte de Galice Menendo Gonzalez" but that this was disputed by "Sancho fils de Garcia, l´oncle maternel d´Alphonse", the dispute being arbitrated by "Abdalmelic fils d´Almanzor" who ordered "au juge des chrétiens [de Cordoue] Açbagh ibn --- de décider…[et il] prononça en faveur de Menendo Gonzalez". After the death of al-Mansur, the kingdom of León signed a peace treaty with his son al-Muzzaffar, subsequently providing help to the Muslim troops which sacked Catalonia in 1003. A charter dated 22 Aug 1007 records the judgment given by "Adefonsus rex" in a dispute "in comitatu Cornati et Auiancos", and recounts the history which started "tempore…principis dni Ranemiri prolis Hordonii" between "comites Scemenus Didaci et Arias Aloitici", continued between "dns. Sisnandus eps. proles Hermegildi loco apostolico et domnus Gundisaluus comes proles Menendi" and "post obitum dni. Sisnandi eps…domnus Rudesindus eps. cum nepto suo domno Munino proles Gundisalui", "in diebus dni Veremudi principis prolis Hodonii" between "Didacus et Arias Aloiti…et Adefonsus Eroni…Didaco Gundisaluici et Renamior Gundisaluici comitibus et dns Petrus eps.", and "dux domnus Menendus proles Gundisalui". "Geloira regina" donated property to Santiago de Compostela by charter dated 18 Aug 1017, subscribed by "Adefonsus princeps, Sancia proles Ueremudi, Tarasia proles Ueremudi, Geloira proles Ueremudi…". King Alfonso V confirmed the possessions of Santiago de Compostela by charter dated 30 Mar 1019, subscribed by "Adefonsus rex, Geluira regina, Veremudus princeps…". Sancho III King of Navarre captured large parts of the kingdom of León.
The Chronicon Regum Legionensium records that King Alfonso reigned for 26 years and was killed "by an arrow at the town of Viseu in Portugal", and buried in León "with his wife Elvira". The Chronicon Compostellani records that “Adefonsus filius eius [Veremudi, Ordonii filius]” reigned 29 years. The Chronicon del Salterio, dated to 1055, records the death "IV f[eri]a M i[u]l[i]o era TLXVI" of "Adefonsus rex". An epitaph in the church of San Juan de León [later the convent of San Isidro] records the burial there of “Rex Adefonsus...interfectus est sagitta apud Viseum, fuit filius Veremundi Ordonii, obiit Era MLXV III Non Mai”. 1