ABSTRACT
Medical studies often involve measurements that are collected on unrelated subjects.
However, some investigators are interested in relationships among family members,
especially when studying genetic versus environmental factors. For example, Feng
et al. (2009) proposed an approach for assessing family risk that incorporates the
relationship among family members. Magnus et al. (2001) studied the similarity
of birth-weight between family members (mother-child, father-child, and mother-
father). These authors were especially interested in estimating the father-child cor-
relations, which they reported as being less confounded by nongenetic effects than
mother-child correlations.
