In an attempt to tease out family influences on teenage sexual behaviour, recent literature explores the correlation of timing of sexual activity and childbearing among sibling pairs. Exploring a sister''s influence in the context of high early childbearing, such as one observed in South Africa, could contribute in understanding escalating teenage pregnancies and childbearing. The 1998 South African Demographic Health Survey will be used to analyse the sexual behaviour patterns of young women between 15 and 24 years of age, focusing specifically on their age at sexual debut, and age and the covariates associated with teenage pregnancy. These results show that having an older sister who has given birth to a child during adolescence could influence the age at which a younger sister has a child and her age at sexual debut. From the results sisters could be a strategic population to target for pregnancy prevention, which would help reduce early childbearing and also the spread of HIV and AIDS in Africa.