The brothers came from the Russian Caucasus region and moved to Kazakhstan at a young age before coming to the United States several years ago.
"My youngest was raised from 8 years in America. My oldest was really properly raised in our house. Nobody talked about terrorism," their mother said.
The suspects' parents recently returned to Dagestan in the Caucasus region after living in the United States for about 10 years because they were "nostalgic," the father, Anzor Tsarnaev, told Russian state-run Zvezda TV.
He accused someone of framing his sons. "I don't know who exactly did it. But someone did."
A federal official told CNN that Dzhokar Tsarnaev came to the U.S. as a tourist with his family in the early 2000s and later asked for asylum. He became a naturalized U.S. citizen in 2012. Tamerlan Tsarnaev was not a naturalized citizen, said the official, who spoke on condition of anonymity. He came "a few years later" and was lawfully in the United States as a green-card holder.