I don't know if I can help with that, but I'm curious about why you think he might be adopted.  Maybe you can give me some examples of where the evidence is
assistant
Do you want to just trick him or are you trying to convince him?
assistant
how do i convince my brother he is adopted?
user
That might not be my strongest skill, but I could try.  Why do you think he is adopted?
assistant
I don't but I want to trick hikm.
user