Ragnarok: Requiem for the Lost Ones - Ch. 3

[MangaDex]

 

[Cinnamonalt]

Kathryne is his sister? I recall Egnigem was his sister. Did they change it or am I mistaken?

 

[Mallinock]

As far as I'm aware, Cenia was never noted to be related to Seyren.

Keyron being related to Seyren is a somewhat more recent development. The Ragnarok Zero anime trailer partly implies this relationship: https://www.youtube.com/watch?v=tNBQmihnbqY