Accompanying visa

I have a couple of issues related to accompanying visa. We are located in Bosnia and Herzegovina. My husband lives and works in South Africa since 2011. and he have work visa until 2017. Now, my children and I wont to join him. I understand that my girls (ages 11 and 9) should apply for a study visa.
Which visa should apply my son, who is 19 years old and studying in Bosnia and Herzegovina? Does he must have a study visa or we can look for another visa?
Thank you in advance

Your son should apply for a visa that suits the reason he is going to South Africa. What will he do in SA? If he plans to study, then he needs a study visa.