The names of the deceased have been published by a Afrikaans language newspaper.
This from:
News - South Africa: Harrismith plane crash claims four
"According to Beeld newspaper the victims were Dr Johan Adriaan Venter, an orthodontist from Vereeniging and his wife Elzabe, both aged 61; their son Christiaan and his wife Christine, both aged 29, and both chartered accountants"
Very sad.