Sibling correlations for cranial measurements from serial radiographs.

Sibling correlations are presented for nine craniofacial measurements from lateral cephalometric radiographs of participants in the Fels Longitudinal Study of Growth and their siblings. Because the data were collected serially, measurements on sibs at the same age can be compared at one-year intervals. Sibling correlations are generally lowest during the first year of life and highest as adulthood is approached, but no interpretable pattern is established during the intervening years. Most of the correlations are significantly greater than zero, and many exceed 0.5, the value expected for a completely heritable polygenic trait. This suggests that common sibling environment contributes to sibling resemblance for craniofacial dimensions in our sample.