parent 1 and twin parent 2 was set to 1 for MZ twin parents and .5 for DZ twin parents. Genetic transmission from parents to adolescents was explicitly modeled using the latent factor A1’. The influence of A1 (influence of parents’ genes on their own parenting) on A1’ (influence of that same set of genes on adolescent externalizing behavior) was set to .5 (because children inherit half of their genes from each parent), and the influence of those genes that parents and offspring share on externalizing behavior were freely estimated (A1’).
