If your brother is a US citizen or green card holder living overseas he is still required to file US taxes. He may not owe, but there still is a rquirement to file. As he has not for so many years, he should seek qualified advise as to the best way to go about dealing with back filing.
See this thread on a related topic for more info:
double taxation-- how to avoid? American working in CH
A few years ago when visiting the States, I stopped at immigration, gave the nice man my passport, he swiped it, looked at the screen, and said:
"Thank you for paying your taxes, Ma'am. Welcome back to the United States."
I shudder to think what might have happened if I had not been paid up....
It's never a good idea to mess with the IRS.