Don't understand why Adam and Libby refer to Susan as their Stepmother? Since both of them are adopted, that's impossible. As soon as you adopt a child, you legally become their parent. And thus from a legal standpoint they are no different than a natural born child. So Adam and Libby would call Susan, Mom, instead of Stepmom. She could only be their Stepmom, if Phil was their biological father, and bearing in mind they met as teenagers at University,and Phil clearly didn't have two kids in tow back then, which he would have to for Susan to become their Stepmom. It simply doesn't make any sense to call her that. Adam and Libby are adopted, and therefore Susan and Phil are their mother and father. It doesn't make any difference, whether they're biological or not. Because once adoption is completed, in the eyes of the law, they legally become their natural parents.
If the Dev wanted to make Susan and Phil Step- parents, then he should have set the game up, with Libby as Susan's real daughter and Adam as Phil's real son. Because that is the only way it can work. As far as Libby is concerned, the existing back story already gives a possible explaination for such a storyline with Susan getting raped during one of the scenes. That would then explain why Susan and Phil didn't get together at University till later, giving Phil time to have his own relationship with some other girl, giving him Adam, with Adam's mom then tragically dying from some fatal disease or accident or whatever. That way both of them could be step-parents for each others children. Seems to me the Dev has gone to a lot of trouble to make this game into a more realistic slowburner, so why not apply some equal realism to the parent's relationship with their kids? Because at the moment it doesn't make any sense. And everytime, Libby and Adam refer to Susan or Phil as Stepmom or Stepdad, it's just really irritating, because you know it's not true.