How Well Do Half-Siblings Get along?
Bernstein (1989), in a qualitative study of stepfamilies who had reproduced, found that relationships were better when there were larger age differences between halfsiblings, when the stepfamily had been together longer, when half-siblings lived together, and when children were similar in temperament. Which parent is shared may also matter—although in a Dutch study half-siblings showed lower levels of investment in each other than did full siblings (Pollet, 2007), maternal half-siblings invested more than did paternal half-siblings.
Half-siblings who live together all of the time or most of the time generally think of each other simply as siblings (Anderson, 1999; Bernstein, 1989; Ganong & Coleman, 1988). The “half’ is a meaningless abstraction to these siblings, and they do not refer to each other as half-brothers or half-sisters. However, when children have little contact, distinctions between half- and full-siblings are more common; in these situations, the “sibling” part of the label half-sibling is the meaningless abstraction (Bernstein, 1989). More research is needed on nonresidential halfsibling relationships, but the few studies that have been done lead to the conclusion that residential half-siblings function similarly to siblings. Ahrons’ (2006) longitudinal study of postdivorce families found that over 90 % of those who had halfsiblings think of them as brothers or sisters. Even though the average age discrepancy in Ahrons’ study was large (10 years), and at the time of the half-sibling’s birth the older half-siblings in her sample thought it was weird to have a new baby in the family, these sibling relationships developed to be positive ones. Ahrons reported that the amount of time spent together as children did not affect their perceptions of half-sibling relationships as adults, and the gender of the shared parent also did not seem to matter.
Some interest has been shown on the percolator effects of half-sibling relationships on other family relationships. The rationale is that because a child born to the stepfamily couple is biologically related to everyone else in the household, this shared genetic connection will help to facilitate integration as a family unit and will draw the marital dyad and step-relationships (e.g., stepparent-stepchild, stepsiblings) closer (Ganong & Coleman, 1988). As we mentioned in Chap. 5, our study of concrete babies, inspired partly by self-help books that indicated a remarried couple having a child together would help cement family bonds, did not support this assertion (Ganong & Coleman, 1988), although parents in Bernstein’s (1989) study felt that having a mutual child helped them as a couple. This finding may be due to cognitive dissonance (“we did this, so of course it was a good thing”) or social desirability.
Research findings on the effects of mutual children on other family relationships are generally mixed. For example, investigators found that the presence of a halfsibling negatively affected the stepmother-stepchild relationship (Ambert, 1986; Santrock & Sitterle, 1987), increased mother-child conflicts (Schlomer et al., 2010), positively affected the stepfather-child relationship (Ambert, 1986; Hobart, 1988), was not related to stepmother-stepchild ties (Ahrons & Wallisch, 1987; Ganong & Coleman, 1988; Hobart, 1988), had little effect on stepfamily relations (Ahrons & Wallisch, 1987; Booth, Brinkerhoff, & White, 1984; Ganong & Coleman, 1988), had a negative influence on older children’s behavior (Zill, 1988), and reduced the amount of time mothers had to spend with their children from prior marriages (Ahrons & Wallisch, 1987). Some of these discrepant results may be explained by differences in the timing of the assessment; half-sibling relationships may be more stressful when children are younger than when they are older (Bernstein, 1989; Ganong & Coleman, 1988). Also, the amount of time since the half-sibling was born may make a difference, if children are still adjusting to the birth. Researchers generally have not examined potential moderator variables that could influence the effects of half-siblings on other family relationships (e.g., age differences, gender combinations, amount of contact, and other variables related to family structure). In addition to these structural variables, unexamined intrapersonal variables such as temperament, expectations, and reasons for reproducing in remarriage are potentially factors in determining the quality of half-sibling relationships and the effects the mutual child has on other relationships. Most studies simply investigate the presence/absence of a half-sibling in a family as the sole predictor for relationship quality variables.
Information about half-siblings could have important implications, especially for those stepfamilies most likely to reproduce: younger, postdivorce stepfamilies in which one of the adults has not been married or reproduced before (Bernstein, 1989; Ganong & Coleman, 1988). Despite inconclusive evidence regarding the concrete baby effect; adults in stepfamilies continue to have children partly to strengthen stepfamily bonds.