User blog comment:Ncduru/The Erza-Irene Connection/@comment-94.220.75.45-20160425140440

I also think the scar has a meaning. Wasn't there a chapter where Porlyusica mentions that the surgery of Ishgar is not as quite good as in other 'countries/contintens'? Maybe she is Erza's sister and had also some kind of tumor, 'cause her magic was too strong when she was a baby. (Like Ultear) So her parents, or one of them, or a friend took her to Alvarez to cure her, but never returned with the baby for whatever reasons.

At least Eileen/Irene must know about having a sister, 'cause why would Neinhart mentions somethig like 'Lady Eileen's...'when she never told a story about having some king of relative somewhere. Or he had some kind of sixth sense then.

Or It's really her mother and she had a bad cesarean. The fahter then may took Erza to Ishgar and remarry maybe. I'm really curious about her.