My father’s mother was born Rebecca Joseph, according to my mother and brother. I have not been able to find any information about her under that name, though, and as such, I have found no information about her parents and little verifiable information about her siblings.
A couple of weeks ago, I discovered an alternative last name. The birth certificate of my uncle Ben from 1907 lists his father as Samuel Saporky and mother and Beckie Fakir. That must be them, but Fakir is not Joseph. “Fakir” is Turkish for “Poor”, so maybe she was just saying in Turkish (which she may have been) that they were very poor, and that was put down on the birth certificate.
Now, I have found information about what appears to be the marriage license of my grandparents. In 1904, Philadelphia recorded the marriage of Samuel Separisky and Rebecca Hirsh. Again, that seems to be them, but now there’s the name Hirsh, not Joseph or Fakir. Here’s another lead for me to search immigration and marriage records for her siblings.