User blog comment:B214/Volume 23 discussion blog/@comment-31137559-20170320082729/@comment-9595671-20170320170348

We have heard Ophis call Issei her father, and Rias and Akeno her mothers.

So does that mean it's been confirmed Ophis and Lilith see each other as siblings? I haven't checked to see if any translations for Vol 22 have come out yet, nor an update to their sections in each other's relationship pages.