Sibling relationships differ from other relationships, in that they change in different stages of an individual's life. Sibling relationships are affected by various factors such as gender, age gap between siblings and number of siblings in a family. Whether positive parent-child relationships contribute to positive sibling relationships, or whether sibling relationships can compensate for parent-child relationships is still controversial and debatable. Parent-child relationships in relation to sibling relationships were explored in this research. Various studies have suggested that siblings influence each other's social and cognitive development. However, most of these studies have focused on sibling relationships in infancy. Siblings may also influence on each other in adolescence. This study focuses on sibling relationships in adolescence. In Hong Kong, siblings tend to study in the same school. The effects of siblings studying in the same school were also explored in this study. This study aims at studying sibling relationships in adolescence, understanding the factors influencing these relationships, and exploring how these relationships influence siblings' learning.