For those having issues triggering the Foursome:
1 - You need to have the threesome with the sisters going on already. This happens after you are way into the game and go massage Jill (older sister).
When you ask Jill to give her a massage, tell her to get naked and have sex with her. At one point Lily will start to show up asking if she can join or watch.
2 - You will need to make the mom share the bed/room with each one of the sisters and, at night while they are sleeping, ask to join them in bed.
First the will be an option to ask for the mom to give you a handjob (while the three of you are on the same bed). After that, it will give you an option to have sex with her. In both cases the sisters will make it clear that they know you (mom and you) were having sex, so there is nothing else to hide.
You have to do that for each sister. So make mom share bed with Lily, and then make mom share bed with Jill.
3 - After having sex with mom, while they are sharing bed with your sisters. Share bed/room with Jill and, at 20:00, do the massage. When you start having sex, Lily will ask to join, you agree and, at one point, the mother will show up and you have the foursome.
I'm still having issues with the "anal" scene with Alexa (younger step sister).
Edit: Apparently in order to evolve Alexa you always need to do the Selfie part. I didn't even have the blowjob option. Let's see what goes from here.
Edit2: Yep. That was it. have the scene now.
