can a biological child from a good home have RAD?

Have you really looked at a RAD checklist, to see some of the really weird behaviors that are linked in the same person? Does your sister have those? She may have some sort of attachment spectrum situation, w/out being full-blown, too. Or she might have something(s) else, as the other poster mentioned.Then again, I know a family where the first child was wanted, the second was not, and that was palpable even to outsiders. Also, different children have different temperments, some are easier for parents to get along with, and vice versa. Most of us have seen that many times. So, lots of factors can influence attachment.