Introduction Research on children relationships takes three divergent routes. The research on parent–child relationships focuses on how parents establish and/or maintain relationships with their children. The second approach entails how children form relationships with their peers in different social settings such as schools. The third approach, which is the main focus of this thesis, is on children relationships with their siblings. This kind of relationship exists long after the demise of one’s parents and long before one meets his or her spouse. In this sense, it may be regarded as the longest relationship that people form in their lives. It determines children social competences and their capacity to resolve conflicts positively. Hence, the connection is critical in their emotional and cognitive developments (Kennedy, & Kramer, 2008, p. 568). Using peer-reviewed journal articles, the current thesis begins with a discussion of the general informational and historical background of sibling relationships. It then discusses psychological impacts of sibling relationships, their differences across cultures, factors that influence them and their effects on siblings. In the last section, the thesis addresses the ways of ensuring closeness in sibling relationships. General Information and Historical Background Most people are brought up together with sisters and brothers. Sibling relationships are characterized by conflicts, intimacy, rivalry, and warmth during childhood, adolescence, and adulthood (Dixon, Reyes, Leppert & Pappas, 2008, p. 119). The type of sibling relationships depends on different factors such as attachment levels, the environment in which children are brought up, and family constellation. For example, the process of modernization and industrialization increases social mobility such that siblings become detached from one another with time (Knigge, Maas, Leeuwen, & Mandemakers, 2014, p.549). Attachment between children and their parents has a powerful role in the development of social-emotional traits at childhood. Ward, Vaughan, and Robb (1988) posit that parent-child attachments predict future child competences and interaction behaviors with peers and siblings (p.643). There is scholarly contention that early children relationships are critical in determining their identity and personality. Since parents and siblings form the first relationships with infants, there has been intense interest in studying the influence of parents and sibling relationships on psychological development of children from infancy and early childhood through adolescence to adulthood (Kolak, & Volling, 2011, p. 214). Psychoanalytic approach to family relations forms one of the earliest attempts to explain sibling relationships. This school of thought is associated with psychologist Sigmund Freud. Sigmund interpreted sibling relations as a manifestation of Oedipus complex. Under the situation, male siblings compete for maternal attention while female siblings compete for the attention of their fathers. Although contentious, psychologists such as Alfred Adler assert that siblings build their personality through struggles to gain significance from their parents and that birth order is an important determinant of the development of sibling personalities (Boll, Ferring, & Filipp, 2005, p. 155). Psychologist David Levy suggested in 1941 that siblings