Do you mean twin studies where the twins are separated at birth and raised by different parents? This is a rare thing for parents to do so I think you are exag

Do you mean twin studies where the twins are separated at birth and raised by different parents? This is a rare thing for parents to do so I think you are exaggerating when you say there are "countless" twin studies saying family environments don't matter? I would be surprised if there were more than a few such studies? Or are you claiming something else?