I reckon they're both Vampires of some kind, although which kind regarding their type of immortality and needs(Western or Eastern, most likely Eastern derivative) I'm uncertain of. They definitely do not fear sunlight or anything of the sort, and they can apparently live off regular food just fine if Tia is any indication. It definitely seems similar to
Vampire Knight where they were separated and she lost her memories of being a Vampire. I doubt they're siblings this time, though.
At the very least, from her dream back in chapter 9 and her subconscious etiquette that she seems to possess, it's clear that she was once a noble woman from another country. The clothes she had in the dream was of a more Eastern design, whereas the clothing of the Kaios empire is Western. Also, it's likely(or rather, obvious) that the Emperor is the other person in the dream. As such, this would suggest they are both from another country, which begs the question: how did he become the emperor in the first place? Did he impersonate a prince and rise to the throne or did he take it by force? We know he only recently rose to the throne, and if what Blesse said is true then it's been at least one year since he became King which happened before he turned the kingdom into an empire. And another question, how did they get there in the first place? Were they traveling and got separated? Or did they get transported via a magic portal due to some random misfortune?
There's still so much information we don't know, yet they've teased us with quite a lot at the same time. This author certainly knows how to entice readers.
...the emperor reminds me of someone that had a pretty bad reputation for being....... a bad person, but he didn't allow his underlings (or anyone) to molest one family where he lived because he really respected them, especially the father, for being a honest man... Pretty contradictory right?
Does she have the same condition as the Emperor? Why is no one around? owo
Haha Blesse is a cutie but a smart cutie, I really like her, she can sweep from one to other without problem and I'm glad someone as trustworthy as her is Tia's personal maid now