User blog comment:Derax-Pagani/Chapter 507: Voice/@comment-7418318-20161024164611

Hey, new theory!

Erza and Irene were simese twins and that's where Irene got her scar from. Erza had her scar removed by Proly when she got her new eye. The age difference comes from the seven year timeskip.

Wait a minute... I meant it as a joke, but now writing it out it actually makes some sense. oO Weird...