Finally, if you ask me. Took freaking long for the corruption to set in.
I guess I'm in the minority of enjoying seeing the family mind controlled by a third party shadow organization to fuck for unknown reasons, seeing their lives played with rather than of their own choosing.
That said, for conscious fooling about, I think with Aiden (father, uncle) should have been the last to fall. Abi and Oli, after being pumped full of horny gas (but not full mind control) eventually having a bi-curious moment with each other, fooling around and eating each other out/making out, and Aiden catching it on camera and being shocked but horny from it, I think could work.
Crosses that taboo incest threshold, but since they're full of that horny gas, and they weren't raised together or knowing of each other, it'd be easier for them to cross that "evil" taboo boundry, it would be not as reinforced in their mind.
That could also help Aiden fall for it too, seeing his two sexy nubile charges go at it.
If Mia was still around, her banging Oli that way would also work. Hell, it's not incest for her at all, though fucked up regardless.