Ok, i agree with both sides.
Starting with the side that they act dumb:
They are around 23-28 mentally, they should have some ground of knowledge. Especailly because they had modern kowledge about life. They should atleast be more aware of their surroundings. Even if they were abused, they should still be more smart. In fact they should be more wary of strangers rather then their familes. Their family has been taking care of them, feeding them, clothing them, protecting them, etc, why are they wary of them. Rather they should be more wary of the duke and his son, but they are not, for what reason?? They also just are unable to think straight, I think they should act like their age whether abused or not.
I think their justified to act that way:
The children were abused!! Image living a life - Dying - being abused for 5 years - you are brought to a strange place. You have noone that went through the same hardships. Then you have your other family, when your only family, your mom, abused you for 5 years. They should be wary of their family. Your family never answer your questions, then someone that your family trusts, comes along and promises to answer your questions. I mean their family talked about them behind their back. Why woudn't you trust the person that seems trustible and answers all your wonders? I think they have a reason to act how they act.
;) im still simping