Yes there is a Path to getting with Mia... As for the Step-Mother, you can only watch her Masturbate at this point, but I'm sure the path to bedding her will open up as the game advances...
As for the play-by-play to get you to Mia, I'm not going to spoil that for you... Play the game and get there... Just know that your stats matter, keep playing around with them as you play through...