Half siblings are brothers and sisters who share only one biological parent and are thus, half biologically related. Although half siblings may be the result of extramarital/partnership affairs or post-bereavement, most are the result of a divorce and remarriage. Half sibling research is rare, and existing research and even national and international statistical reporting agencies often incorrectly conflate half siblings with stepsiblings. Research that can be found on half siblings often illustrates a “deficit-comparison” approach where half and stepsiblings are compared to full biological siblings and studied for how they fall short of biological sibling outcomes. Early research speculates that children who reside with half siblings experience poorer educational outcomes, report significantly more depressive symptoms, exhibit poorer coping skills, are more likely to engage in risky behavior such as early sexual activity and drug and alcohol use, and have more strained sibling and parental relationships compared to those with no half siblings or those with only full biological siblings. The challenges that exist for half sibling relationships are often hypothesized as associated with either family structure (half siblings located within a complex stepfamily) or explained through evolutionary perspectives of Darwinian fitness. However, research on half siblings overall is mixed, with studies also positing these outcomes are not due to the presence of half siblings and that there are instead positive implications from having a half sibling on individual outcomes, sibling relationship quality, and overall family functioning. Overall, half siblings can form quality relationships and half brothers and sisters who share a residence, are closer in age, of the same gender, spend more quality time with one another, have parents who prosaically intervene on their behalf, and who emphasize their positive relationship and connection through addressing terms and sharing backstories of their family’s origins are more likely to report a positive relationship.
