There's a phrase from Chinese novels that really applies to this one
"Making wedding clothes for other people's children"
I just don't see the entire, I've got my memories back let's reduce myself and my parents who love me to peons. Also so far the adopted brother is a piece of crap who is just looking out for his lottery ticket (who do you think is the only person in place for a coupé d'etat?) . The sister is questionable.
Really breaking off the engagement, kicking out the step brother stopping the donation and then tossing tax relief seems a much better strategy