How do I find out if someone in my family was adopted?

Why are you making it your business?

You ask.

DNA testing (by mail).

Haha I would agree with all of the above. If this person has confided in you that they think they might be... and the want to find out. Well. I guess it is in between that person and their parents. That person can only legally find out if they is over 18. BUT only that person is legally allowed to find out. You or anyone else cannot get those records.
If that person is 18 and does want to find out, it is a legal process to get those kind of records found and released. IF they are there.

I had a son whilst I was stationed in England and am trying to trace him. I have his original birth certificate. I know that his Mother put him in care when he was a few months old and then went on to get married and have another child, I have tried searching for her through records [which I found] but have come to a standstill - perhaps she emigrated. I have received confllicting stories about my son as his Mother was a big liar. One is that he was very ill and not supposed to live - I searched death records = nothing. I am now at the conclusion that he was adopted but how do I find out?
Don't judge me harshly, at the time of his birth I was in Viet Nam, it was when I came back my searching began.