The only scene i got where you after pretty much following the Layla path backs off suddenly is for Alexis, you get 3 options, break up Layla, same thing with Alexis and lie to both of them(doesn't turn out so well lol).
Nothing in relation to Nikki, other than looks of jealousy.
Good points about Nikki, i'll add another thing for her:
She's been through this already, having to deal with her sister having the same feelings for the MC... other girls that she doesn't even know?
That's nothing, she will throw her hat in the ring regardless.
Erynn is hesitant to open up due to past experiences, that's why (i believe) she wants the perfect romantic "made for each other" experience rather than just jump the MCs bones out of hornyness.
There's definitely some stalling (i feel like Nyx wants to finish telling her story before "allowing" sex), the MC could've already invited her to do something, but it is what it is, the game doesn't allow us to invite her to a restaurant/movie/whatever and have a light hearted date with her.
The why didn't they talk ever, is kinda explained in the story that he was behaving like a dick, she tried but he was purposefully avoiding her... not a great explanation how he managed to avoid her for a month(must be great at sneaking huh) but yeah, that's how the game explained.
The mom scenes seem to be down to sense of humor of the dev, Nyx keeps getting asked about incest, "will the mom be on the menu?" and she's taking a piss.
Honestly, given how far along the game already is, it would be a brutal 180 for her to go from normal mom to "porn logic" mom now.
We've only seen Layla/Alexis dad from the back, never his face, he has the same black hair as Navarro but there's not much else to go on...
Navarro is with 99,9% certainty married to Gabi after what we hear from Gabi at the sports event.
Even for this game legalized poligamy would be a major stretch... we see that Gabi is in fact married not just a side thing for Navarro(she has her own side thing in fact lol).
And Principal Moore also lives with her husband, i'd say her husband can maybe be brother or cousin to Navarro, but not Navarro himself.
That would make Layla/Alexis our cousins... but maybe that's a "crossable" incest line, someone more informed on Patreon rules can clarify this.
Gabi and Val... remains to be seen, maybe 10 years apart sisters, fits better than mom in my opinion.
And i'm a big supporter of the John>Erynn idea (with Iris as a bonus).