Truth

I am confused about something related to adoption...according to BV it's better if truth is told to the kid when he learns to handle it but how do we know how will adoption truth affect the child...every child is different...some may just forget about it and lead the life as it is but some may feel suffocated and eager to know about his real parents and even feel discrimination in small matters...this quuetion arised in my mind when orphanage warden ahd told Shiv to tell the truth to child after s/he matures but becoz of Shiv's past mystery i forgot to make any topic in it...so what do you think...is it really beneficial to tell the truth to child or it all depends on child's maturity level?