I am an adoptive parent of an adorable little boy whom I love with all my heart. I also have a biological daughter who is already grown up and married
The thought of telling him that he isn't my biological child is difficult, but, it's his right to know. Lies have a way of coming back to haunt. It's not fair to him not to tell him.
We get to guide our children through their growing years, but, once they reach adulthood, they have to live their lives and hopefully apply the things we taught them. But, they'll never again be "ours" as they were during their growing years.
However, no one can ever take the joy of watching them grow and develop from us. So, even when or if my son goes looking for his biological family, the childhood years I had with him are mine. And, wherever he goes, whatever he does, he'll know that my husband and I are his parents, who love him with all their heart, unconditionally. And we weren't afraid to tell him the truth.
Another thing.. We also have a friend, a young man who was adopted as a newborn baby. When I asked him what I should tell my son, he looked at me and said "The truth. Never lie to him".
Hopefully I made sense..