The purpose of this study was to examine the relation between sibling relationships, life satisfaction, and the loneliness level of adolescents with regard to gender, order of birth, and sibling dyads. The study group consisted of 382 (209 female, 173 male) students in total, who were studying at high schools (regular high school, vocational high school, Anatolian High School, private colleges) selected from Karsiyaka District in the city of Izmir, Turkey. The data collection tools used were the Life Span Sibling Relationship Scale, Life Satisfaction Scale, and Ucla Loneliness Scale III. The multivariate analysis of variance (MANOVA) was used for the analysis of data. The results from the research demonstrated that gender, birth order, and sibling dyads led to significant differences in life satisfaction, level of loneliness, and sibling relationships. In line with the results obtained from the research, it could be recommended that sibling relationships in the Turkish culture should be examined in terms of various age groups and different variables, and their psychosocial consequences should be subject to research.