My father was born in the Netherlands, moved to SA in 1959, but became a South African citizen before I was born in 1967. My son (27), however, wishes to apply for Dutch citizenship. Is this at all possible?
Is this at all possible?
Probably not. For your son to be a Dutch national, there must be an unbroken chain of Dutch nationality from your father, through you, to your son. There are provisions for former Dutch nationals to regain their Dutch nationality, but it seems likely that you are not a former Dutch national, and even more likely that your son is not.
This is because your father probably lost his Dutch nationality when he became a South African citizen. He would not have lost it, however, if he was under 21 and was naturalized independently from his father. There might be other exceptions as well. For example, under current law, a Dutch national can take the nationality of his or her spouse without losing Dutch nationality. I believe that such an exception existed for women but not for men in the 1960s, but you might want to look into that more closely.
If your father was Dutch when you were born then you were Dutch when you were born, though as noted above this seems unlikely. However, even if it were the case, you most likely would have lost your Dutch nationality on your 28th birthday because there was a law in effect from 1985 causing the loss of Dutch nationality for an adult who (a) has dual nationality, (b) was born in the other country of nationality, and (c) lives for 10 years in that country. So, assuming that you were born in South Africa and lived there continuously until your 28th birthday, you would have lost your Dutch nationality (if you had had it in the first place) at that point.
In 2003, the 10-year rule was changed. Now it is triggered by 10 years of residence anywhere outside the Kingdom of the Netherlands (including both its European and Caribbean territory) or the EU, but the 10-year period is reset by receiving a Dutch passport or declaration of nationality (Verklaring van Nederlanderschap). So if you lived outside South Africa and therefore did not lose your Dutch nationality before 2003, you would have lost your Dutch nationality in 2013 unless you had received one of those documents in the meanwhile.
There is another exception to the 10-year rule, which is that if you were married to a person who was working for the Dutch government or an international organization to which the Netherlands belongs (for example, the United Nations), then the 10-year period does not apply.
EDIT: I forgot to extend this analysis to your son. If you were Dutch when you were born in 1967, your son would have been Dutch when he was born, because you would have been around 25 when he was born, and you would not yet have lost your Dutch nationality.
However, if you lost your Dutch nationality before he turned 18 (roughly in 2010) then he would also have lost his Dutch nationality at that point (unless his mother were somehow Dutch and retained her Dutch nationality). If, however, you somehow remained Dutch until after he turned 18, then he would be a Dutch citizen today, and therefore eligible to receive a Dutch passport. This seems very unlikely, I think you will agree, but if it is the case then he should act quickly, because if he is Dutch now, he will lose his Dutch nationality at his next birthday unless he can get a Dutch passport or declaration of Dutch nationality before then.