Please don't give up on them, from what you've said they've had a very rough time, being molested and neglected isn't a walk in the park you know!!
As hard as it may be, keep on with the communication, don't show them anger, the poor children probably feel they can't do anything right so what's the point in even trying?!
I know it's not easy on you and your wife to be but try and understand where these kids are coming from, I suggest lots of family communication, counselling and take advice from social services if need be!
The reason these kids are like they are is because they feel scared, which is understandable after what has happened to them and they feel nobody wants them!
Please do keep up with therapy sessions and one day you will get a breakthrough! Remember they are only children, scare and vulnerable ones at that! Don't give up on them, show them that you're willing to listen and be there for them, I know it's difficult but try and not show them anger, if they do something you don't like they may be provoking for a reaction, don't give it, count to 10 and think about what to say/do before doing it!
I wish you a lot of luck with it, it won't be an easy road to walk but it will be worth it, try and see from their point of view and don't give up on them!
All the best! xx