Shared environment is probably not created equal though. While the family environment is constant, parents are likely to vary (deliberately and/or not) in their resource allocation (e.g., attention and care) among their kids. An interesting recent paper shows that the non-inherited genetic material of the parents may _still_ have an influence on the kid. [0] What exactly accounts for that influence remains to be elusive, and it would be quiet astonishing if the majority of the influence can be explained by well-established (or rather, exhaustively studied) behavior patterns in psychology. For example: birth order, number of same-sex siblings etc.