And what are y'all referring to?
Zofia never said she isn't her aunt,she said she doesn't like being called "Auntie" due to being only five years older.
Since it'll probably never be explained in full,the best theory is that Zofias' family married into the same generation as Margarets' and Marias' grandparents,with Zofia born shortly afterwards,either with some of the Nearl bloodline or as part of an extension elsewhere.
Hell,it could be even further back then the grandparents if we really want to be wide apart,explaining even how Margaret couldn't be sure.
What we do know is that all kinds of cray cray happened and Zofia is now practically in charge,ignoring the dead beat office working member,leaving most of the choices to the servants.
And after the events,we now have a second happily family being all snuggly on Rhodes Island.