They only spent TWO years together. How TF is that call 'Raised Together'. IN BOTH TIMELINES TOO. Eugene became head at early age so in both timelines he didn't grow up with them. Hari was spent SIX years by the Vastias compared to the TWO years with the Ernest. And Hari was only similar to their late sister by her hair colour (hers is a shade darker) and age. She only got adopted by them. I reread the story in bits. And she still has vivid memories of her real mother. She still attached to her blood mother even though she knows that the Ernst is her "parents".
And she didn't marry Johan in the previous timeline. They met twice and at their second meeting they planned to get married. Then she died before the marriage.
There are many definitions depending on region, culture, etc . But incest GENERALLY refers to sexual relations with blood family. Which Hari is not.
Eugene and Hari clearly have a special relationship. They don't view each other as siblings.
I guess the part where Eugene comforted Hari and said she's their sister was a bit off. But I feel they said that as if to support Hari and convince her that she's not alone and they wouldn't abandon her. Maybe in Korean it wouldn't sound weird.
Dongsaeng means sibling, can also be referred to someone who's younger than you and you are close to them. Like for e.g. Oppa or Noona. Both are use for elder brother and sister, but can also be used by someone younger who is unrelated to you but close. To you.
And she is part of the Ernst household, they adopted her. But doesn't mean they are coming a huge sin like incest concerning all the points I mentioned above.
Is Blanche 11 year's old?
Spoiler......
Spoiler: mirror guy is apparently/approximately her age. A prince from another kingdom cursed to be trapped in a mirror
And living with my 11 year old sister. I don't see how that could be any of a reach.
Although she's pretty immature for her age.
However people in the past, in general, were much more developed in maturity compared to people of the same age today.
I'd say in maturity of action, not necessarily in terms of emotional maturity and perhaps not in terms of naivety (particularly in the upper classes).