Responses
I've read the novel, they ain't related *spoiler^
Rezef and Cayena r only half-siblings through their mother, Rezef ain't anything to the emperor. His dad is Raphael's dad. So basically the empress funked around with the Duke and created a love child, however Cayena and Raphael r not related as they don't share parents its just that one of their parents happened to fuck the other

Wait...so all her love interests are her siblings?!?!?!?!? BOTH ML’S?!? ARE YOU KIDDING ME, PLEASE SAY NOOOOOOO