Other historians list Himiltrude , described by Einhard as a concubine , as Charlemagne 's first wife .
Other historians list reorder his subsequent wives ; accordingly Luitgard is sometimes numbered as his first wife .
Other historians list Himiltrude , described by Einhard as a concubine , as Charlemagne 's first wife , and reorder his subsequent wives ; accordingly Luitgard is sometimes numbered as his first wife .