A year into Paul Whelan's detention in Russia, his family's focus remains on bringing him home, especially now that they're increasingly worried about the state of his health.

The former U.S. marine, who holds Canadian, American, British and Irish citizenship, was detained in Moscow on espionage charges on Dec. 28, 2018 while visiting for a wedding.

His twin brother, David Whelan, says the family maintains it is a wrongful detention.

"I think our biggest concern right now is that we know he has a hernia that was supposed to be operated on last spring, in early 2019," Whelan told CBC News.

"That's a condition that can become an emergency condition at the drop of a hat, particularly because he's been waiting nine or 10 months since that surgery was supposed to happen."

David Whelan, who lives in Newmarket, Ont., north of Toronto, hasn't been able to speak to his brother because he says Russian police have blocked Paul's access to a phone.

He says Russian Ministry of Health doctors saw his brother in August, and agreed that he needed hernia surgery, but his condition has deteriorated during his imprisonment and there has been no plan to schedule an operation.

"Our concern is that there's really no way for him to get the kind of medical care he needs there. He's not able to speak to English-speaking medical staff so we can't get any information on what his health currently is now."

Canadian government response

"Canada is extremely concerned by the detention of a Canadian citizen, Paul Whelan, in Russia," a spokesperson for Global Affairs Canada told CBC News in an emailed statement.

"Canadian consular officials are providing consular services to Mr. Whelan and his family," the statement reads.

The email goes on to say that the government continues to work with its allies on the case and is calling on Russia to ensure detention is not used as a political tool.

When asked if officials were aware of Paul's health condition, the ministry said: "Due to the provisions of the Privacy Act, no further information can be disclosed."

Before Christmas, a Moscow court extended Whelan's detention until March 29, but his brother anticipates he'll be held much longer.

David Whelan, Paul Whelan's twin brother. says his family has been doing everything they can to advocate for his release. (Evan Mitsui/CBC)

Despite calling the current situation a "repetitive cycle of detention hearings," Whelan says he does not feel defeated even though more than one year has passed since his brother was arrested.

"We will continue to work just as hard for Paul. I think we always have hope that he'll come home. The hope is that it will happen sooner than later. But it will happen."