I have a foster son, who today loudly and quite seriously proclaimed that he's not my real kid. He's lived with us for over a year, and we are most likely going to adopt him, having started the paperwork to do so. I normally don't care much if he talks about his birth parents, or if he calls me by my first name, but for some reason, this just bothered me today. Thanks!
Don't worry about it. That's a really common behavior with foster kids. Here are a few of the many reasons why:
Or, it could be any number of other things. Don't sweat it. :)