Since the number, age, and sex of one’s brothers and sisters can constitute an important factor in one’s life, we gathered the relevant data from those we interviewed. We have counted as siblings not only those genetically related, but also any other children reared in the same home with the subject.
The families with the smallest number of children were those from which came the homosexual offenders vs. adults and the aggressors vs. minors: the average (median) individual came from a theoretical family of 3.7 children including himself. The largest families were those in which the incest offenders vs. adults were reared, the number of children being 6.1. The prison group was intermediate, and the control-group figure was 4.4. No groupings or trends of consequence were noted in this matter of family size.
Taking the numbers of individuals with families of various sizes, we calculated the probabilities of a person being the eldest, youngest, or an intermediate child. We than compared these ex pected probabilities with what our subjects reported. The agreement was generally quite good, but there were three glaring discrepancies: the homosexual offenders vs. adults, the aggressors vs. children, and the peepers had too many of their members being the youngest child. The “fit” between probability and report was also not too good for the aggressors vs. minors, but this may be the result of small sample size. Aside from the exceptions mentioned, it would seem that birth order is unimportant in this study of sex offenders.
Similarly unimportant is whether or not an individual was an only child or in any case reared alone. There is a positive correlation, naturally, between family size and the percentage of persons who were only children. The proportion of only children ranges from 3 per cent (for the incest offenders vs. minors, who came from the second largest families) to a surprising 22 per cent (for the aggressors vs. minors, who came from the smallest families). The control and prison groups are around the 10 per cent level.
In investigating the matter of the gender of siblings, we devised a ratio showing the number of brothers per 100 sisters, with the subject excluded. Immediately evident is the fact that the majority of sex offenders have an unduly large proportion of brothers. The control group is nearly evenly balanced with a 101.5 ratio, and the prison group is not badly skewed, but 11 of the sex-offender groups had more brothers than the control group. Only four groups, the offenders vs. children and the three aggressor groups, had more sisters than brothers. Aside from this trend toward masculine siblings no important generalizations can be gleaned from these ratios.