Anna Catherina Elizabeth Du Preez (Bezuidenhout) - Anna connected to incorrect parents?

He had 4 daughters. My mother in law, Bettie Van der Merwe had 3 sisters. Tannie Anna Venter, Tannie Lief (ACE) du Preez, and Tannie Maggie Pienaar. There still was another sister who died at birth and was buried at Skeerpoort while he was working at the Hartebeespoortdam. We are going to look for the grave, as I know it was near Skeerpoort railway station and next to the train tracks. My husband said that he saw the graves when he was still working as a train assistant. I want to take a photo of the grave with the baby's full names and date of birth and death and open a profile on geni.

The article refers to 3 daughters and one already deceased. Mrs Anna Venter died in the early 70s, the article above was +- 1978.