Ann and Lisa are close to innocent womens in Big Brother.
They really weren't.
As soon as Lisa saw Max's magic dick, she was already well on the path to having it inside her, and had no real issue with the fact that they were brother and sister. She was all too happy when Alice was "blackmailing" them, and even if you chose Olivia to be Max's GF, she was more than happy to be involved in a pseudo-threesome where her own brother was a part of it, because she would happily get herself off watching her own brother fucking Olivia.
Ann was basically the same, and there's history with her own sister too, and the guy who abducted her which left her with a fetish for submission play, and cared more about what society would think of sexual relations with her son, more than actually having sex with him. Not to mention she was so fucked in the head, that Eric easily had her doing things his way, with Max being the only obstacle by virtue of being the Player Character.
That entire family is one big perverse, freaky mess. Kira and Alice are the two most honest with Alice being second to Kira, but only just.