The "Corónicas" Navarras name (in order) "don Pedro…el rey don Alfonso, que ovo nombre Remón Belenguer et el conte don Pedro de Provença et el conte don Sancho et a la muller del rey don Sancho de Portugal" as the children of the "conte de Barçalona…en esta su muller [dona Peyronela]", stating that the first named Pedro died in Huesca. The Brevi Historia Comitum Provinciæ names "Ildefonsum primogenitum" as son of "Berengarius comes Barchinonæ et Provinciæ, maritus Petronillæ".
Betrothed (30 Jan 1160) to Infanta dona Mafalda de Portugal, daughter of Afonso I King of Portugal & his wife Mathilde de Savoie. A Chronica Breve names "dona Mafalda" first among the daughters of King Afonso I, adding that she married "comde Reymon de Barcelona" (although this source is inaccurate in other details).
He succeeded his father in 1162 as RAMÓN Conde de Barcelona, Girona, Osona, Besalú, Cerdagne/Cerdaña and Roussillon. "Ildefonsus…rex Aragonensis, comes Barchinonensis, duc Provinciæ" granted "vicecomitatu de Carlades", held by "avus patris mei Guilbertus…comes", to "Hugonem comitem Rutenensem" by charter dated 1167. He founded Teruel 1169-72. He secured the vassalage of Marie Ctss de Béarn 1170. Comte de Roussillon (including the see of Elne) in 1172 on the death of Guinard II Comte de Roussillon without heirs.
He succeeded his mother in 1174 as ALFONSO II “el Casto” King of Aragon. He secured the vassalage of Centule Comte de Bigorre 1175, by granting him the Val d’Aran. He conceded Murcia to Castile under the treaty of Cazola Mar 1179, retaining Valencia within the Aragonese sphere of influence. Roger II Vicomte de Béziers-Carcassonne confirmed his vassalage Nov 1179. He succeeded his brother in 1185 as ALFONSO I Comte de Provence (declaring himself Marquis de Provence), appointing Roger Bernard Comte de Foix as procurator. He acquired Pallars Jussà 1192 by cession of Dolça de So. He ordered the compilation (completed 1194) of the Great Book of Fiefs (liber feudorum maior), an administrative register of property, under the direction of Ramón de Caldes, dean of Barcelona cathedral. Betrothed to Matilda or Teresa, daughter of Afonso I King of Portugal (-1218).
The Chronicle of Alberic de Trois-Fontaines records the death of "Hildefonsum rex Arragonum" and his burial "in abbatio de Populato". The Gestis Comitum Barcinonensium records the death in 1196 of "Ildefonsus" and his burial "in Monasterio Populeti" which he had founded. The Crónica de San Juan de la Peña records the death of King Alfonso in 1196 aged 42 and his burial "al monasterio de Poblet". The "Corónicas" Navarras record that "el rey don Alfonso de Aragón, fijo de conte de Barçalona" died "al yssient de abril", in 1234. The Anales Toledanos record the death in Apr 1195 of “el Rey D. Alfonso de Aragon”. The Thalamus de Montpellier records the death in Apr 1196 of "Namfos rei dAragon a Perpinhan". 1