Considering that Evelyn leaves the game early if you push a bit too far too quickly, would it be possible to set the Evelyn leave variable so that she doesnt appear in the game at all?
Evelyn plays a big part in the story, so I do not see that as being possible.
Probably better off changing it slightly so that either the MC or Evelyn were taken in as a child, but no direct family relation.
Not adopted, but simply given a place to live.
A patch could then revert it back, if the end user chose to use one.
That way, MC and Evelyn still act like siblings because they grew up together, but they are not related at all, without the patch having been added.
Think of it as Wesley and Buttercup from the princess bride in some ways.
He was a poor servant, so loving buttercup was not something that he could easily admit to, and the same goes for her. She couldn't easily admit to loving a servant.
It would have been socially unacceptable for Evelyn to marry a servant, which could be used as the reason for her reluctance in getting into that kind of relationship with him..
This could make changing it a bit easier, since it would mostly be just a change of text.
The MC simply lived with her uncle and her until he was old enough to take on a skill that would support him. While growing up, he acted as a servant.