Board Thread:Theories Discussion/@comment-25886565-20150812203149/@comment-4134422-20150813010108

I wouldn't exactly say that Irina didn't know it was a HER, she knew Kirill and her were alike in other way than just siblings. Quote Servant from the Fifth Pierrot novel thread:

'' "Our speaker (Irina/Julia) therefore felt deprived of her brother since Elluka had made him different from what she was. She herself was a HER and continued hiding it from Elluka." ''

She may have meant it as "ghoul child", though.