There are various ways that children can be subdued so that they can't fight back. I'll leave it at that. And please note that I've not named names nor accused anyone of any crimes. I specifically am focusing on little Max and the specifics of his death.
So, who do you think would have conducted one of the "various ways" of subduing Max prior to his fall? There was supposedly only one other person in the house, a 13 year old. Are you saying she did it? If not, then you ARE either saying Rebecca did it and murdered Max or Rebecca and her sister are covering up for someone else. I think you should at least outline the possible "whos" in your conjectures if you are going to continue to make them.