"It's real," Tsarnaeva said, according to Kilzer. "My son knows all about it. You can read on the Internet."
In the spring of 2010, Zubeidat's eldest son got married in a ceremony at a Boston mosque that no one in the family had previously attended. Tamerlan and his wife, Katherine Russell, a Rhode Island native and convert from Christianity, now have a child who is about 3 years old.
Zubeidat married into a Chechen family but was an outsider. She is an Avar, from one of the dozens of ethnic groups in Dagestan. Her native village is now a hotbed of an ultraconservative strain of Islam known as Salafism or Wahabbism.
It is unclear whether religious differences fueled tension in their family. Anzor and Zubeidat divorced in 2011.
About the same time, there was a brief FBI investigation into Tamerlan Tsarnaev, prompted by a tip from Russia's security service.
The vague warning from the Russians was that Tamerlan, an amateur boxer in the U.S., was a follower of radical Islam who had changed drastically since 2010. That led the FBI to interview Tamerlan at the family's home in Cambridge. Officials ultimately placed his name, and his mother's name, on various watch lists, but the inquiry was closed in late spring of 2011.
After the bombings, Russian authorities told U.S. investigators they had secretly recorded a phone conversation in which Zubeidat had vaguely discussed jihad with Tamerlan. The Russians also recorded Zubeidat talking to someone in southern Russia who is under FBI investigation in an unrelated case, according to U.S. officials who spoke on condition of anonymity because they were not authorized to discuss the investigation with reporters.
The conversations are significant because, had they been revealed earlier, they might have been enough evidence for the FBI to initiate a more thorough investigation of the Tsarnaev family.
Anzor's brother, Ruslan Tsarni, told the AP from his home in Maryland that he believed his former sister-in-law had a "big-time influence" on her older son's growing embrace of his Muslim faith and decision to quit boxing and school.
While Tamerlan was living in Russia for six months in 2012, Zubeidat, who had remained in the U.S., was arrested at a shopping mall in the suburb of Natick, Mass., and accused of trying to shoplift $1,624 worth of women's clothing from a department store.
She failed to appear in court to answer the charges that fall, and instead left the country.
Seddon reported from Makhachkala, Russia. Associated Press writers Eileen Sullivan and Matt Apuzzo contributed to this report from Washington.
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