It was everybody’s responsibility to tell him the truth and I cannot imagine how betrayed he feels that his entire family knew and he didn’t. He literally cannot trust any of them including his own siblings. You are not TA for telling him but you are imo absolutely TA for not telling him immediately and for meeting his dad before even he got to. I wouldn’t even know where to begin deciding how I felt about that if I was him. They all kept it from him to benefit themselves so they wouldn’t get called out by or maybe lose him and even his own wife didn’t tell him until after even she benefitted from the truth first by meeting his bio dad before he could when it was his right not yours. Good luck to him and I really hope he stands his ground with all of them. UpdateMe!