The only clue I'm aware of is in Chapter 8, when Ophelia is breastfeeding Sterling...
Sterling: "Is it wrong for me to have a good time?"
Ophelia: "Morally...kind of...legally...I'm pretty sure..."
Sterling: "Actually this is one of the states where it's legal between adults..."
Ophelia: "I see I'm not the only one who wants to burn their search history...and please take this seriously..."
They're obviously talking about incest. According to
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, it appears the only US states where this is legal are New Jersey and Rhode Island.