Hi Norman
This was my grandmother's twin sister. However, some of the information is incorrect.
This is the correct information:
Elsje Sophia Johanna (my grandmother known as Ella) and Susanna Catharina Jacoba (known as Suzie) were twins, born on 4.4.1913 to Christiaan Johannes van der Heever and Susanna Catharina Jacoba Rautenbach. Note that it is Van der Heever and not Van den Heever.
My grandmother married Andries Stefanus Cronje and aunt Suzie married Johannes Jakobus de Wet.
Susanna Catharina Jacoba de Wet nee Van Der Heever and Johannes Jakobus de Wet only had one child, a daughter named Sonia. That is my aunt.
In other words Susanna was her mother and not her daugther.