The setting is a modernized fantasy world, roughly equivalent to the present day, and I'm trying to double-check the mundane bits to have a good foundation for the fantasy bits. Though the social care system I've dreamed up so far (as well as the "modernized" country overall) has definite American influences, input regarding other countries might also be helpful.
I have a character in the equivalent of his teens who was found as a newborn and bounced around in foster care ever since, with no family located, and I'm figuring the probability of his never being adopted. When he got older he developed violent tendencies and assorted emotional problems, but I still have the issue of why he wouldn't have been adopted as a baby, especially since I gather babies are usually in higher demand than older children.
So far: He was discovered in a state of health consistent with premature birth and resulting complications (underweight, etc.) - though probably not too premature and not too serious complications, since he's quite healthy at the time of the story and survived without medical attention for several hours until he was found (in a well-kept-up transit station during early summer, if that matters). Also, he's - I guess the closest real-world analogue would be an ethnic minority (that is, minority species). Most people in the region aren't blatantly prejudiced, but there is some amount of quiet friction.
In the reality of whatever country you're familiar with, in this day and age, would you consider these plausible reasons for his chances of adoption being low? If not, what other ways might there be to account for this? And in general how likely would it be for someone to grow up entirely in foster care from birth (or close to it)? If this would be a really extraordinary case I need to take that into account.
Googled mainly various combinations of: adoptability/adoption, adoption rates, infant/infancy, premature birth, minority, placement.
Thank you for your time.
ETA: Okay, I think I've got this sussed. Thanks again, everyone!