Earlier this week, NPR asked John Sipher, a former member of the CIA's Clandestine Service who worked in Moscow, whether Whelan fits the profile of an American spy working inside Russian Federation - to which Sipher replied, "Absolutely not".
"We are relieved and very pleased to know that staff of the U.S. Embassy in Moscow have been given consular access to Paul and confirmed that he is safe", his brother, David Whelan, said in an emailed statement on Friday.
Paul Whelan was arrested by the FSB state security service on December 28. The security service has not given details of the case.
"We are relieved and very pleased to know that staff of the USA embassy in Moscow have been given consular access to Paul and confirmed that he is safe", the family's statement said. The family first discovered he was detained through media reports.
Whelan received a "bad conduct" discharge from the Marines, according to his official military personnel file obtained by Fox News. This detail, made public after his arrest, was a surprise for the family.
Mr Whelan is a retired Marine who has British citizenship through his parents. He moved to the U.S. as a child.
Britain's Press Association said Whelan's United Kingdom citizenship was reported by the us embassy to British officials on Thursday. Canada's CBC News says that while it has not gotten direct confirmation of his citizenship, it received a statement from the government's Global Affairs Canada saying, "Consular officials are aware that a Canadian citizen has been arrested in Russian Federation". The conversation was set up after he met with the USA ambassador to Russian Federation.
"We are giving every support we can, but we don't agree with individuals being used in diplomatic chess games", he continued.
US Secretary of State Mike Pompeo said this week that the United States had asked Russian Federation to explain Whelan's arrest and would demand his immediate return if it determined his detention is inappropriate. "We're not ruling out any theories at all at this stage as to why this might have happened".
Whelan's Russian defense attorney, Vladimir Zherebenkov, is convinced his client is innocent.
In addition to convicting him of attempted larceny and bouncing checks, the Marine Corps also found Whelan guilty of falsely using another person's social security number to sign in the online training system Marines access to complete courses that can advance their rank and pay.
Putin has previously stated he would rein in Russian retaliatory measures against US interests in the hope relations would improve, but Whelan's detention indicates the Kremlin's calculations may now have changed.
Russian media reported Thursday that Whelan had been formally indicted for spying and the Interfax news agency said he denied the allegation.
CBS suggested that the ex-Marine "is a pawn in Russia's play to get back one of its spies, Maria Butina", though the Russian student was not actually charged with espionage. Whelan's twin brother said he doesn't believe Whelan is a spy.
Many in the West question whether the arrest was in retaliation to USA conviction of Russian gun rights activist Maria Butina.