I have a problem with one of my husband's ancestors. His great grandfather's birth cert shows HIS parents as Joseph Ballard and Hannah D'arcy. His siblings, born before and after him show the parents as Joseph Ballard and Hannah Fawkes.

The 1881 census with widowed Hannah Ballard and two of her children shows she was born in Stroud, Glos. Research has shown Hannah Fawkes was born in Bisley, Glos (near enough) and the right age etc. There is no trace of a Hannah D'arcy at all...anywhere.
I think great grandfathers mum was Hannah Fawkes, which means the name on the birth cert is incorrect......
Has anyone else come across anything similar? Are mistakes made on certs?
Beverley