Katrin - I agree with you that children should not be lied to and if you do lie to them they may never forgive you. I also had the privilege of being a foster mother (three kids from foster care, two of my own) so I know a little something about the challenges and rewards involved with that.

However, I was adopted and found out about it quite by accident when I was 16 and had been sent away to reformatory and read it in my psychological records. I'm sure my adoptive parents thought keeping it from me was the right thing to do, and secrecy about such matters was also probably the norm at the time. Be that as it may, my disagreement with you is your statement that "all children need to know who their biological parents are ..." Perhaps most children do, but personally I have never had any interest whatsoever in knowing who my biological parents were. I am sure they had their reasons for putting me up for adoption, and that's that. My adoptive parents were plenty okay for me, warts and all.