Maret Tsarnaeva, who lives in Toronto, told CBC News by phone Friday that she hadn't yet contacted her brother Anzor, 46, who is the father of the two men, Tamerlan and Dzhokhar Tsarnaev.
"My nephews cannot be part of this terrible, horrible act that was committed in the streets of Boston," she said.
"I know these two nephews — smart boys, good boys — they have no motive for that. They have no ideas to be going to this kind of act. It's just not the case, it cannot be true."
Tsarnaeva said she has lived in Canada since 1996 and had studied at the University of Manitoba, obtaining a Canadian law degree. She said she hasn't seen her nephews for five or six years.
However, she said she spoke to the oldest, 26-year-old Tamerlan, two years ago when his daughter was born, and then again a year ago.
She said Tamerlan is married to a woman that she described as a Christian, and that he's been staying at home taking care of his daughter while his wife worked. About two years ago, she said, he became more interested in his Muslim faith, and started praying five times a day.
Tsarnaeva said she isn't ready yet to believe Tamerlan is dead. She also said she spoke to someone at the FBI on Friday morning to tell them she believes there is no evidence against the the two men and that they are innocent, but that authorities have not contacted her.
It's because of the Chechen connection, she said, that her nephews are being targeted, but she pointed out that the two had spent only a year in Chechnya when the family attempted to move back. Dzhokhar was a toddler at the time, she said. Once war broke out, they left and eventually ended up in the U.S. as refugees in 2002.
Tsarnaeva said she keeps analyzing and thinking about the evidence authorities have on her nephews.
"They are allowed to walk on the streets of Boston," she said. "They live in Cambridge, Norfolk street, which is five minutes from the cross-border between Cambridge and Boston. It's Monday, they are walking, maybe, you know, walking around for their business. Backpacks? How can this be suspicious, carrying backpacks? At the age of these boys."
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Tsarnaeva, who became a Canadian citizen in 2003, explained that there are four lawyers in her family: herself and three of her siblings, including Washington lawyer Ruslan Tsarni.
"And now he is being questioned about these two boys who he admired so much," she said. Ruslan Tsnari has been telling American television stations that he wished his nephews never existed.
Tsarnaeva said that her brother Anzor, the father to Tamerlan and Dzhokhar, lives in Makhachkala, the capital of Dagestan, a a republic in southern Russia. Dagestan borders on Chechnya.
Tamerlan, she said, visited Makhachkala a year ago.
She described Anzor as "very soft-hearted", a man who, when their father was "blown to pieces" in an unexplained incident in a car in Kyrgyzstan, was "paralyzed" with grief for four days to the extent that he couldn't move. She also said that Anzor was the victim of a beating on the streets of Boston, adding that she did speak to him a month ago.
Tsarnaeva said the family was born in Tokmok, Kyrgyzstan but their ethnicity is Chechen. Chechens, she said, have always been persecuted. "All together, we've been tossed around. Deported from here as Nazi collaborators, then there, then here. Enough," she said, her voice raising. Her siblings became lawyers, she added, "to protect ourselves."
When the FBI released pictures of the two suspects Thursday night, Tsarnaeva did not see them and only learned of her nephews' involvement Friday morning. As the interview ended, she seemed to be reeling from the news, murmuring, "My God, my God, my God."