Carol and Colin,
I might be able to clear things up a bit about the Polka/Oliver relationship.
Marlene Polka shared Carol's family record sheets with me. I've also transcribed my great- grandfather George Frank Oliver's journals (1899-1921) in which he mentions the Polkas throughout. It's given me somewhat of an idea about how my family's relationship to the Polkas.
My great grandmother was Eligia (Mora) Oliver,(1858-1923), born to Eulogio "Juan" and Louisa (Morin) Mora in Nacogdoches, Texas. Two of her sisters, Lucinda Mora and Mauricia "Mary" Mora married Polkas. A fourth sister was Pauline "Polly" (Mora) Espitia.
My ggrandmother Eligia Oliver had a daughter named Mary Louisa Oliver (whose name I think gets confused with Mary's), but she was never married to a Polka as far as I know.
Reducinda "Lucinda or Cindy" Mora was born to Eulogio "Juan" and Louisa (Morin) Mora in Nacogdoches, Texas March 1, 1851. She married Frank Polka Sr. in 1867 in Victoria. Their children were Frank Jr., Louis, Rosie and Sophia Polka.
Mauricia, "Mary" Mora was born to Eulogio "Juan" and Louisa (Morin) Mora in Nacogdoches September 21, 1855. She married John Polka in 1871 in Victoria. Their children were Emma, John, Alex, Mary Louise, Frank, Fredrick, Francisco (not sure) Joe, and Henry.
The Mora family history is interesting. I have recently become a member of the DAR and have documentation of my Mora lineage which traces back to Antonio Gil Ybarbo, founder of Nacogdoches.
Hope this helps with your research!
Pam (Oliver) Fanelli