My understanding (in about nutshell size)
Warning Spoiler (if not already read to ch 25)
☆Both families are superstitious
☆They believe that a persons luck is determined at birth by the stars they are born under, ie some combination the astrological phenomenon and the birth date
☆The 2 heirs (the purple hair and fiancé) were born with disaster level of luck that will cause ruin to their respective families
☆Jingxi was adopted to counter act the bad luck for purple hair
☆The grandfather of the fiancé worked out that if Jingxi were to marry the fiancé that it will counter act his bad luck.
I never would have picked that up, thanks.
I must ask, though, where did you get this from? I didn't see any mention of stars or the like. Was it in the raw?
Just posting again since I'm still not sure and wondering what your source is.
It's mentioned multiple times right from ch 1 that she has the fate of a Queen as per her time of birth - basically astrology type superstition.
Why don't they let the purple-haired daughter marry him if she likes him so much? I originally thought they adopted her so that their own daughter could have some freedom, but if she wants him then why not give her to him instead? Is it because she hasn't been trained to be as "refined" like her adopted sister was?