Simplified representation of the children-of-twins model. In the given example the (adult) twins are sisters. The genetic transmission (left hand side) is fixed at .50 because parents and children share 50% of their genome. The other set of genes that influence the child trait (bottom left) are genetic influences that explain variance in the child trait but not the parent trait. The crucial test for presence of environmental transmission is whether the p-path is significant. Note that ‘child’ can refer to child or adult offspring. See for the full and detailed model McAdams et al. (2018).