Table 2 shows cross-sibling within-trait correlations by sibling type and gender. The cross-sibling within-trait correlations could not be calculated separately by gender for sexual maltreatment given the very small number of respondents who reported sexual maltreatment (e.g., among MZ male twin pairs, only 8 individuals endorsed sexual maltreatment). Since MZ twins share 100% genetic similarity whereas DZ twins and full siblings share on average 50% genetic similarity, greater cross-sibling within-trait correlations among MZ twins than among DZ twins and full siblings suggest genetic influence on a trait. Children’s genes appear to have a small effect on composite maltreatment, which is driven largely by female pairs. Children’s genes appear to have a larger effect on neglect. Interestingly, the pattern of correlations for physical maltreatment across genders suggests an influence of children’s genetics. However, no such influence is suggested by the physical maltreatment correlations within gender (note that although the male DZ physical maltreatment is lower than the MZ correlation, the full sibling correlation is not). Children’s genetics do not appear to be related to the sexual maltreatment they experience. The MZ correlations are well below one for each maltreatment variable, suggesting nonshared environmental influences and/or measurement error.
