Paul Whelan, a former U.S. marine arrested in Russia on espionage charges, was visiting Moscow over the holidays to attend a wedding when he suddenly disappeared, his brother said Tuesday.
Whelan, 48, who is head of global security for a Michigan-based auto parts supplier, was arrested on Friday. In announcing the arrest three days later, the Russian Federal Security Service said he was caught "during an espionage operation," but gave no details.
The Russian spying charges carry a prison sentence of up to 20 years.
Paul's twin brother, David Whelan, who lives in Newmarket, Ont., told CBC News the allegations don't ring true to him.
"He has a background in law enforcement and is a marine and travels regularly ... he's not the sort of person who stumbles into a strange environment or makes poor choices that could cause him risks," David Whelan said.

The morning of his arrest, Paul Whelan — who had been to Russia several times previously — took a group of wedding guests on a tour of the Kremlin museums, his brother said. David Whelan said the last time anyone heard from the ex-marine was at about 5 p.m. and then he failed to show up that evening for the wedding.
David Whelan would not comment on why he thought Russia had taken his brother into custody.
"I think it's too complicated to come up with a simple answer. I think there are many reasons and it could be completely arbitrary. Our goal is to get him home," he said.
No contact with family
David Whelan said his family has been in contact with U.S. Embassy officials, but there is little information on his brother's status until a 72-hour blackout period lapses and they can have access to him.
He said the family intends to contact U.S. officials in Paul's home state of Michigan.
David Whelan also said his brother, a U.S. citizen, previously held Canadian citizenship, but he was unaware whether he remains a citizen of Canada. He said the family has not been contacted by the Canadian government.
Watch David Whelan speak to CBC News Network about his brother's arrest: