If I recall correctly, AA's brother and sister were brought in to identify her after the
Berliner Nachtausgabe story was published in 1927. At first both her brother, Felix, and sister identified her as being Fransiska. She then spoke to her brother privately, after which he changed his story and said that she wasn't his sister. Fransiska's sister had a minor outburst at the end of the session, yelling something along the lines of "I know you are my sister! Admit it!"
I'm recalling this from memory from Robert K. Massie's
The Romanovs: The Final Chapter, so forgive me if some of the exact details are incorrect, but I believe the gist of the story is right.
What became of the Schanzkowska siblings, and were they ever sought out by an intrepid reporter in the many decades of later fascination with the Anna Anderson story? I would love to hear more details about these people.
Also, I wonder what transpired in the conversation between AA and her brother that caused him to change his mind? I imagine it would have been something like "Felix, these crazy people think I'm a Russian Grand Duchess, and they're feeding me, clothing me, and putting me up in castles. Don't ruin this for me!"