Pretending that your child is not adopted or withholding that information from an adopted child may be the single most disrespectful thing a parent can do to their child.
In essence, the act of withholding that information is a statement by the adoptive parent’s that the act or state of being adopted is, in of itself, what causes a child to feel alienated from their family. By withholding that information an adopted child will feel like they are “truly” part of their adoptive family. Lastly, the statement implies that adopted children are somehow less a part of ones family and by not acknowledging that they are adopted the child will feel more naturally (pun-intended) a part of their family.