Max being a "teaching aid" so that Ann can teach Lisa about matters relating to sex - handjobs & oral, leading to choosing who you want to suck & swallow Max.
Lead up to (with Kira's advice) and payoff for Max having sex with Ann... By having sex with Ann, I mean all over the house, several times a day, with Lisa & Alice practically catching them at it.
Tied into the new Ann stuff is more Alice stuff, where she "blackmails" Max & Ann, leading to being able to fuck both of them on the couch side by side, fucking Ann on the couch with Alice watching & masturbating, spanking Ann (either Max or Alice), and Alice showing how jealous she is that Max is deep dicking their mother more than her.