A couple thoughts off the top of my head. In Chapter 3 the redhead sister gets thirsty for other dudes. Even with NTR off, the dialogue with her indicates that Max is not enough for her anymore, and that she is looking elsewhere for some fun.
She also likes to bang some of Max's other ladies when he is not around.
Also, Alvin, I think? Max's friend who wants to bang his Mum. Even with NTR off they are hanging out in bed together almost naked for a lot of chapter 3. This is highly distressing for folks who don't want to share their ladies.