You talking to the birth parents sounds like a no-win situation. You could tell your son his birth "father" called and asked about him. I assume that there are protocols wherever he is in jail for sending letters and making phone calls. If the biological "father" calls you again, you could simply say, that you will give your son the message that he called. Even if your son is manipulative and is talking down on you to his birth "parents", your son still knows what is true and what isn't true, even if he isn't speaking the truth -- he will remember how you treated him and raised him, and even if he misrepresents that to these people, he will also know he is misrepresenting that. In the end, I don't see how a relationship with these people at this point in his life would feel anything other than awkward. He might want to communicate with them at first, but that is probably more because he is desperate and is grasping at straws.
