Unfortunately the two remaining Aunts now have Alzheimer's and so I rely on notes, info from Dortmund Archives, and a cousin for the following:

In response to below questions:
My Grandparents were considered stateless on their WWII ID cards and deportation records. My Grandparents moved to France after they were married in about 1924 and unsure what their citizenship status was there - hence my original post. My mother and her sisters were born in France, so French citizens.

Family still in Germany were French in 1921, Prussian in 1936, French in 1941. 

An Uncle who survived (born in Germany) was considered French Jew by the Germans on papers as well as his displaced person ID but it was later changed to German Jew by US officials because of a letter from Dortmund (1949) stating his parents were both German.

Debby Painter

To the original poster - 

It is not entirely clear from your wording, so I'm asking this for clarification: In 1941, who was considered stateless by the French government? Was it your mother and your sisters? Or was it only your father from Poland? Also, can you clarify which individuals were deported in 1941, and which were able to stay in France?

It sounds like the German government considered your mother to be a French citizen simply because she was born on territory in 1905 that was ceded to France after WW I. However, it seems like the French government in 1941 considered your mother to either be a German citizen (because she was born in territory at the time part of Germany in 1905) or stateless because she and her family had fled Germany for France.