How does one find a birth location?

Hi Robert:

Look at https://www.familysearch.org/tree/person/sources/GZGG-DHN - here various census records for your father are attached, which consistently report that he was born in Austria. Sister Fannie was born around 1903 in New York, so your father and his parents must have emigrated from Austria sometime between 1900 (his birth) and 1903. More exact details on exactly where in Austria they came from will probably require finding their Ellis Island immigration record.

Likewise, your mother's census records can be found attached here: https://www.familysearch.org/tree/person/sources/GZGL-1BN. These records show that she was born in New York, shortly after the family had come from Austria and shortly before they moved on to Passaic, NJ.