This thesis consists of three empirical studies, focusing on adolescents' educational and occupational aspirations, and exploring in particular the influence of sibling configuration and family background. In the first paper, we apply multilevel mod- elling techniques to sibling data on further education aspiration and attainment from the British Household Panel Survey (BHPS). We find that firstborn adoles- cents are more likely to attend further education compared with their later-born siblings; and adolescents with a wide age spacing among their siblings than those in a close-spacing sibship. Further investigations show that the first born advantage in further education attainment can be partially explained by birth-order differences in educational aspiration. The second paper examines the effect of birth order on occupational aspiration. Based on Holland's vocational themes, we find that firstborns are more likely to aspire to investigative and conventional occupations, whereas their later-born siblings prefer enterprising and artistic occupations. From a hierarchical perspective, the analysis reveals that firstborns have higher aspiration prestige scores. The effects of birth order on occupational aspiration can be partially attributed to birth-order differences in school performance. In the third paper, we conduct an empirical analysis of the dynamics of occu- pational aspiration in adolescence using multilevel growth models. Our results indicate that adolescents constantly adjust their occupational aspirations with age, in line with the general labour market demand and particularly their own cognitive ability. We find that adolescents with lower socioeconomic status (SES) have lower initial occupational aspirations compared with their relatively privi- leged peers. Further, the differences by SES increase with age, reflecting a growing social class gap in adolescents' occupational aspirations.