It would have been illegal for them to have claimed a dependent child exemption for Barry. This has nothing to do with custody, as you previously insinuated and continue to incorrectly insinuate.
All you know is what we ALL know NOW. In 1973, the woman who zero claims was his mother and the man who he claimed was his stepfather NEITHER OF THEM claimed him as a dependant. And that’s all you can know.
I think it might be best for all of us if you go your way and I go mine, and never our paths shall cross, I won’t address you on a thread and you do the same for me, nothing personal, but our twains shall never meet, you are so locked into what is written down that words and numbers on paper are your little gods, and I follow what people say and how they behave, in all their cheatin, lying, duplicitous ways...you read a book for clues and I read the people.
I believe Ann could have claimed Barry on her 1973 tax return if she was sending money for his support to her parents and it was more than half what it cost to maintain him.