The primary source which identifies Adalhard as the son of Liuthard has not yet been identified, although the testament of "Gerardus [comes]" names "consanguinitate, affinitate et propinquitate etiam nobis junctis, id est Leufredi et Adalardi Comitum".
Seneschal of Emperor Louis I "le Pieux". Nithard says that he "cared little for the public good and tried to please everyone…and ruined the kingdom altogether". The Breve Chronicon Epternacense names “Adelardus comes” as abbot of Echternach from 850 to 856. "Adelhardus comes" was "provisor monasterii S. Maximini" in Jul 855. "Hlotharius…rex" donated property "in pago Eiflinse in comitatu Matfridi" at the request of "Adalardus et Matfridus…comites" to "vassallo præfati Matfridi Otberto" by charter dated 28 Jun 856. An agreement between Charles II "le Chauve" King of the West Franks and his brother Ludwig II "der Deutsche" King of the East Franks dated Jun 860 names "nobilis ac fidelibus laicis…Chuonradus, Evrardus, Adalardus, Arnustus, Warnarius, Liutfridus, Hruodolfus, Erkingarius, Gislebertus, Ratbodus, Arnulfus, Hugo, item Chuonradus, Liutharius, Berengarius, Matfridus, Boso, Sigeri, Hartmannus, Liuthardus, Richuinus, Wigricus, Hunfridus, Bernoldus, Hatto, Adalbertus, Burchardus, Christianus, Leutulfus, Hessi, Herimannus, item Hruodulfus, Sigehardus".
The Annales Bertiniani record that "Carlomannus, Hlodowici regis Germaniæ" sought refuge with "Adalardo, Yrmintrudis reginæ avunculo, suo autem propinquo" after he was banished by his father following his rebellion in 861. The Annales Bertiniani record that "Adalardo Yrmintrudis reginæ avunculo" was "propinquo" of the brothers Udo (ancestor of the Franconian Konradiner family), Berengar and Waldo who were expelled from Germany in 865, and in a later passage record that "Adalardo…et suis propinquis Hugonis et Berengario" fought the Vikings in 865. "Leudo episcopus et Adelardus comes missi dominici in comitatu Augustidunense" heard a dispute between "Vulfaldum episcopum et Heccardum comitem" concerning land at Perrecy, the proceedings recorded in a charter dated to [866/75]. Charles II "le Chauve" King of the West Franks confirmed the donation of property "in pago Alsense...in uilla Blanziaco...et in pago Belnense...et in uilla...Possionis...et in Montelio...et in uilla...Vasmaro...et in pago Augustodunensi...et in pago Belnense in uilla Nolaico" made by "Adelardus comes et abbas cœnobii Sancti Symphoriani" by charter dated 16 Jun 866. 1
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