User blog comment:Glen Gable/The two newest Spriggans II/@comment-62.113.29.75-20161027115728

Maybe there is a third person behind Erza and Eileen... like with brain, he had a second personality inside himself, maybe it's the same with Erza and Irene, although they don't share the same body, Irene left Erza before Tenrou arc and that's why she looks older.