Also the two daughters (Chloe and Hannah) are in Chloe's bedroom, up the hallway, and so my bet is that the "rift between families" will involve Chloe and Heather, once Chloe discovers what the MC has been up to with her mom.
After what has already taken place between between Carol, Heather and Hannah, as well as their apparent relaxed attitude towards "sharing" the MC amongst themselves and with others, it's difficult to imagine any of them falling out about the MC and his sex life.
The Chloe character however looks set for a fall.