Eldgarde was the daughter of unknown parents. The date and place of her birth have not been found.
Her husband was Ithier de Mercœur. They were married, but the date and place have not been found. Their eight known children were Ithier (c0850-c0895), Gauthier (?-?), Vualfade (?-?), Odilon (?-?), Odalric (?-?), Blismodis (0868-?), Vuade (?-?) and Étienne (?-?).