Robert George Londt has a sibling (Henry Frederick Londt) whose birthdays are 162 days apart.
Both Robert George and Henry Frederick's baptism records reflect the recorded birthdates, but Robert George baptism takes place quite late and in Cape Town with a CT address while the family were working and living in Stellenbosch.
I suspect Robert George may be an adopted family child and not the biological child of George and Elizabeth Londt.
I am unable to find out anything more on Robert George... no marriage record or death record.