The four armed men entered the house in Dirk van Deventer Street on Friday evening and first opened fire on Linda Coetzee, 43, who was shot three times in the head and both arms.
She has lost her right eye, reported Beeld newspaper.
Her husband, Kobus Coetzee, 46, was shot three times in the stomach.
Ruaan Coetzee, 21, and his girlfriend, Rozanne Oeschger, were also in the house during the robbery.
He was shot six times and is possibly paralysed.
Oeschger was hit in the leg but managed to run away and call for help.
The assailants sped off when the couple's other son, Dewald Coetzee, arrived at the house at around 20:00.
Only cellphones were stolen.