Right! Here's a solution to tangle of mother and sister shit which seems to be bothering so many.
(1) Heather is William's step-mother (by marriage) but not his (biological) mother;
(2) Chloe was fathered by a man other than William's father and is his step-sister (by marriage) not his (biological) sister;
Under these circumstances William, Heather and Chloe are a genuine (Jerry Springer) family of sorts, which explains their closeness, but William is unrelated biologically to both Heather and Chloe opening up the possibility of intimacy between William and both Heather and Chloe, individually and separately, without such intimacy construed as incest although it would be kind of distasteful, unsavory and weird all things considered I have to admit.
I don't know whether this will sate the incest aficionados but it's the most plausible explanation I can think of that fits.
Can we drop all that whimpering, bleating and hand-wringing about the lack of incestuous content now?
(Because technically there is none.)
Thank you in advance.