Whether or not
@Binfest is correct in their predictions (and I hope they are), let's just look at the evidence of KP's situation.
Carl has not been pictured with any of the children (except Harvey) for many months.
Nor has Katie, apart from some brief shots with her wider family (supervision). They very plainly do not live with her - she doesn't appear to have a fixed abode for a start, and spends much time on the road, so how could she facilitate any of them getting to school, let alone anything else?
We are led to believe (from various sources, not least KP herself letting it slip) that Social Services are involved .
I know from my professional role that SS do NOT remove children from a parent lightly, or limit contact to supervised only, which indicates that there are very serious reasons behind all this.
I presume it is something along these lines that
@Binfest (and others) are alluding to, and that some of it may come out in due course.
I don't know HOW Katie can sleep at night, to be honest. If she's not in a deep depression about this terrible state of affairs then she truly must have some sort of personality disorder, as has been suspected.