My family are looking at travelling to China for a holiday and one of my son's friends wishes attend, what requirements for China visa application for him?

My family are looking at travelling to China for a holiday and one of my son's friends wishes attend. Son's friend is a South Africian passport holder and is under 18 years of age. In addition to the visa application form what additional information is required to process his visa, .i.e consent letter from parents etc