The aim of the current study was to investigate nature of sibling gender differences in relation to prosocial behaviour. The issue of personality was also considered. A Play Form of Behaviour Questionnaire, a Prosocial Questionnaire, a small demographic questionnaire and an abbreviated form of the Junior Eysenck Personality Questionnaire were used on 80 school children who had either an older brother or sister. A cross-sectional design was carried out. The results indicated that females are more prosocial than males and those with older sisters are more prosocial than those with older brothers. The results also suggest that children with older brothers participate in rough and tumble play more often than those with older sisters. The findings of this study highlight the effect and importance of sibling relationships in relation to the development of pro social behaviour.