First, none of what I'm about to say is relevant to actual diagnoses of reactive attachment disorder, oppositional defiant disorder, or conduct disorder. But setting those real mental illnesses aside, it's something I worry about as my wife and I begin the process to adopt older children from foster care.
I was reading a book (don't remember which one) that offered an interesting analogy. Imagine that you have a family, and it's not great: your husband drinks too much, he has trouble holding a steady job, you're often in financial distress, he takes you for granted, your kids are bratty, unruly and ungrateful. You know it's not a model family, but it's your family. You want it to be a better, happier family, but the thought of losing them terrifies you.
Then one day people from the government show up at your door and tell you that they're removing you from your home. They put you in a van and drive you to a different home. They lead you into a strange house and introduce you to the eerily smiling strangers who will be your "new family." They assure you they love you even though you've never even seen them before. They keep calling themselves your "forever family."
Now, maybe they're perfectly nice and very loving. Probably they're a lot different from your "old family" and that is often uncomfortable, whether "better" or "worse." No matter how nice they are, you never really feel like you belong. Inside, a voice is screaming, "THEY'RE NOT YOUR FAMILY!" Whether they're nice or not, this new family has a lot of new rules. You're expected to do lots of stuff you never had to do before, and you're forbidden to do many things you're accustomed to. When you break these new rules, you're "disciplined." They control you, completely. You are powerless.
How would you react? How would you feel about your "new family"? If you're like most human beings, you would rebel, fight, sabotage and resist in both overt and subtle ways. And you would soon come to HATE them.
To me, this seems like a very ordinary human response. And regardless of the neglect and abuse a child experienced in their home, their perception or memory of it may be very similar to this, though perhaps more confused and conflicted. They love their "real family," they want to be with their "real family," and they don't understand why they can't be.
And they resent you. They blame you. From their perspective, how could they not?
Again, far short of actual RAD or ODD, this is something that concerns me. How do you identify the older children who are genuinely ready to move on and really want to become part of a new family? How do you distinguish them from older kids who really just want better living arrangements than they enjoy in foster care until they turn eighteen? I mean, I can't blame that latter set -- I'd want better living arrangements too! Nor can I blame them for being unable or unwilling to discard their "real family" and embrace the new one.
So...how to tell?
I think it is very very important to have a slow transition, one that is appropriate for the child. To maintain contact with the former foster family if at all possible. To be honest with them in all the reasonable ways. To accept where they are at...this is a biggie. I also highly recommend the resources at Creating A Family. Dawn Davenport has so many awesome resources
Here, older children have a say in whether or not they want to be adopted. This is not to say that they won't have the emotions you describe. It is wise to keep in mind that they do have another family that they may love and miss, regardless of what they did to them. Support their feelings and they will trust you more for it.
I don't have any advice for the OP, but I just wanted to mention that the description given of the experience of being moved from one family to another and expected to adjust, be grateful and see these people as a new family is a great one. I think every foster family who takes older kids, and maybe younger kids too, should read and take in. I've seen posts from foster families who are shocked and angry when their foster kids aren't grateful and are still loyal to their useless Biological family. You have to understand it from their perspective and I think the way it was described above was phenomenal!
I love your analogy and I would say it applies to kids of ANY age - not just older ones. Sooner or later that infant that was brought home from the hospital by their new family is going to wonder and wish about their "real" family. I think it's all about how you go about it.
For me - I let my foster kids go at their own pace in terms of what they call me and what I call them. I've seen that make a difference, even though it can be inconsistent - sometimes when he screams mommy he wants me and sometimes he wants her. It's hard to tell.
I never expect my *kids* to be grateful for anything that I do. I expect manners, but I can't mandate or expect certain, specific, emotions. So I think that helps frame my perspective. I also take *any* kid (except for some specific behaviors that I don't feel like I can handle) so I'm not out there searching for a specific kid to complete my family. I saw a lot of that in the classes - families getting licensed to get an older boy because they think their current kid(s) would benefit from an older brother, or a girl because they always wanted to have tea parties.