One reason children in the same family are so different: parental difference in phenotype

Based on evidence from twin and adoption studies, children raised in the same family show little resemblance in cognitive ability, personality, or psychopathology after accounting for genetic effects, indicating that relevant... [ view full abstract ]

Based on evidence from twin and adoption studies, children raised in the same family show little resemblance in cognitive ability, personality, or psychopathology after accounting for genetic effects, indicating that relevant environmental factors result in differentiation rather than convergence within sibling pairs (Plomin & Daniels, 1987). One potential factor underlying sibling differentiation is parental difference in phenotype. Using scores from the BFI-S, a short version of the Big Five Inventory completed by parents and twins in the German study ‘TwinLife’, we assessed whether parents who were more different from one another in their personality ratings had twin children who also were more different from one another. Parental personality difference significantly predicted within-pair personality difference in both DZ and MZ young adult twins; the same pattern emerged but was not significant in the adolescent twin cohort. The pattern was not evident for other traits; parental difference in height and weight did not predict twin difference.

Plomin, R., & Daniels, D. (1987). Why are children in the same family so different from one another?. Behavioral and brain Sciences, 10(1), 1-16.