The mean age difference between full-sibling pairs was 2.2 years (range 0.7 – 6.8). Self-reported maltreatment was assessed during wave III only. Of the individuals from 271 MZ twin pairs (128 male-male and 143 female-female), 397 DZ twin pairs (119 male-male, 104 female-female, and 174 opposite sex), and 1,143 full sibling pairs (301 male-male, 340 male-female, and 502 opposite sex) who responded to the maltreatment items at wave III, 47.7% were male. The ethnic composition, based on self-nomination, was 48.9% Caucasian, 21.1% African-American, 12.9% Hispanic, 6.4% Asian American, and 2.8% Native-American, and 7.8% other. Half siblings were excluded from the analyses because they reported more maltreatment and had greater variance in maltreatment than other participants (results are available on request).
