L&P put a handful of subtle hints throughout AWAM.
On PD 10, while showering with Ellie in the morning, Sophia mentioned self pleasuring. PD 12 - boom, mommy/daughter happy time.
PD 11, after yoga class, Dylan dreams about possibility of having threesome with mom/auntie. Definitely is going to happen on one the routes. I was surprised L&P didn't make her touch nephew's bulge, but she grabbed his butt afterwards.
Gangbang? The way I see it, she'll be open for that with either her beloved boys Dylan/Sam/Zack or Ellie/Patricia/Jules. If someone thinks the latter is improbable, more than likely on PD 16 we'll see Sophia/Ellie/Jules. Ellie is interested in her auntie (evening showering scene on PD 10 clearly indicates that), so adding her childhood friend shouldn't be an issue.
If L&P dares, towards the end of the game movers are coming back, that's one more option.
Ada's kids? Part of this thread would eat their own crap, vehemently protesting, if this ever occurs. It's a frigging VN, chill out, you prudes.
The game is in such an early stage, that closer to the end most of us will be astonished how naughty Sophia has become. Recall the recent jail event, that was her own volition and she surely was having fun.
I'm still in disbelief how many people don't trust L&P's writing skills. He's no Remark, Tolstoy or London. On the other hand, how many trully amazing VN's with the taboo/incest are out there? The Forbidden fruit is sweet and I can't imagine who wishes it more: Sophia or her offsprings.