Sibling types: The influence of genetic relatedness on sibling interactions

Despite demographic trends demonstrating decreasing family sizes, most children grow up with at least one sibling. Family relationships are both social and genetic, distinguishing biological families from all other human bonds. Evolutionary theories are uniquely positioned to explain interactions within the family. The current study utilizes evolutionary principles and theories to explain differences in siblings' relationship quality, affectionate displays, and conflict management tactics for full-, half-, and step-sibling relationships. Full siblings were expected to be more positive, negative, affectionate, and use negotiation and aggression more than half siblings, and half-siblings were expected to be more positive, negative and affectionate and use negotiation and aggressive conflict management tactics than step-siblings. The current study offers some support for evolutionary reasoning for sibling relationship quality and affectionate communication differences. Hypotheses were generally supported for sibling positivity, negativity, and affection. However, hypotheses were generally not supported for conflict management style differences. For siblings' conflict management styles, social learning theories provide a better explanation.