The actor Jack Nicholson was raised with his mother pretending to be his sister. Eventually he discovered his mom was the grandmother. So it can happen.
I still don’t see the name issue from those documents. Maybe it’s because my mother has a legal name she never uses and her nickname and maiden name appear on many legal documents. Doesn’t seem like any conspriacy to me but research on. Maybe Anna will turn up.
SADO or the grandmother still being alive were more interesting theories. Someone found SADO listed as living in NY working for the Ford Foundation after her supposed death date.
I didn't post them JUST for your edification, (that might take YEARS!) there are others on this forum who may be interested in the signatures.