Alice sees herself as a lesbian, so she goes out of her way to wind up her pervert brother. I can quite image some sisters would do that in real life, probably not go as far sexual, but flashing, putting on a show when you know he is perving. Alcohol probably makes her do stuff she wouldn't do normally, it probably doesn't even take much for her to lower her inhibitions and she can just use being too drunk to remember as a defensive mechanism to justify her perversions.
Lisa feels closer to Max than to her mom or Alice as they are close in age and have also slept in the same room for a long time, her mother has suppressed her sexual education so she has these feelings that she can't control and seeing her brothers big cock arouses her and Max is quite good at manipulation by getting her to agree to things. So it's probably a lot of Max's fault that she agrees to go along with her mother, and Eric, finally teaching her about sex. I just started a true friendship game with Eric just to see how far the sex ed between Eric and Lisa will go.
Ann, she's been alone bringing up 3 kids for a long time, they don't have money and by all accounts not much before they are given the house by her ex-husband, she has a new job and someone has finally shown an interest in her. In this aspect I think Eric actually does Max a favour by broadening Ann's sexual horizons. There's no way she would allow Max, before Eric, to sit on her bed and let him watch her have sex or pleasure herself if she wasn't with Eric. I don't think she would have ever punished her kids naked without Eric, opening her up to getting some pleasure from smacking their bare butts. Then there is the part where she sees Max's big cock at the start which obviously, with her probably not having had sex in a long time, turns her on and now that image of his cock is forever seared into her brain.
This game I feel would be better I feel if there was a 'select age' option, as I think most of us know that Lisa is not 18+ and Max is maybe 18, but acts like a 15 year old and do military schools take kids after they turned 18 and especially as its alluded to that Max is over 18, possibly 19, also with Alice, she is 19 tops. if we go by the game trying to make out she is over 20, probably in the region of being over 21, I mean what 21 year old , unless they have a fetish, lets their mom spank their bare butt, especially in front of her pervert brother.
I would say in my mind that Lisa is 14/15/16, Max 15/16/17 and Alice 18/19/20, that feels more believable to me. Add to that Ann would probably be between 34 and 38 tops, if you took her age from what the game is portraying by the ages the kids are then Ann would be 40+.