“I think President [Joe] Biden made the right decision,” David Whelan told MSNBC. “His job is to protect all Americans. It would have been wrong for him to leave behind an American when he had the ability to bring them home.”
Paul Whelan, a former marine and corporate security executive, has been jailed on espionage charges in Russia since 2018, charges that his family and the US government say are unsubstantiated.
Griner was arrested in a Moscow airport in February after officials discovered vape canisters and cannabis oil in her luggage. She pleaded guilty and was sentenced to more than nine years in a penal colony.
US officials said Russia refused to consider including Mr Whelan in the Griner release deal.
“This was not a choice of which American to bring home. The choice was one or none,” said Secretary of State Antony Blinken.
Paul Whelan, 52, was sentenced in 2020 to 16 years in prison as result of what Mr Blinken called “sham charges”.
“I wholeheartedly wish that we could have brought Paul home today on the same plane as Brittney, just as, as the time, I wished we could have Brittney and Paul home when we secured the release of Trevor Reed back in April. But we will stay at it,” Mr Blinken said.
However, the Whelan family fear that it could be years before he is released.
“I think we all realise that the math is not going to work out for Paul to come home anytime soon, unless the US government is able to find concessions,” David Whelan said. “And so I think we aren’t really sure what the way forward is.”
Earlier, on Thursday, an official known to the family visited the home of their sister Elizabeth to deliver the painful news that their brother would remained imprisoned while Griner got to come home.
“Sadly, for totally illegitimate reasons, Russia is treating Paul’s case differently than Brittney’s,” Mr Biden said at a press conference. “And while we have not yet succeeded at securing Paul’s release, we are not giving up. We will never give up.”
Paul Whelan told CNN on Thursday that he was “greatly disappointed that more has not been done” to secure his release.
“I would say that if a message could go to President Biden, that this is a precarious situation that needs to be resolved quickly,” he said in a phone interview. “My bags are packed. I am ready to go home. I just need an airplane to come and get me.”
David Whelan dismissed criticism of the president and said he hoped Ms Griner’s celebrity status would keep the spotlight on his brother and other Americans being held overseas.
“We have got to support Paul. We have got to help him to survive,” David Whelan said. “It is his mental health I worry about. How do you keep up, surviving mentally in that sort of situation?”
Meanwhile, former president Donald Trump posted on Truth Social: "What kind of a deal is it to swap Brittney Griner, a basketball player who openly hates our country, for the man known as 'The Merchant of Death'?
"Why wasn't former marine Paul Whelan included in this totally one-sided transaction? He would have been let out for the asking. What a 'stupid' and unpatriotic embarrassment for the USA!"
Mr Whelan was taken into custody while Mr Trump was in office and a Factbase search of his posts on Twitter shows that he did not once mention the American citizen — even after family members tried to contact him.
David Whelan responded to Mr Trump by tweeting: "Former president Trump appears to have mentioned my brother Paul Whelan's wrongful detention more in the last 24 hours than he did in the two years of his presidency in which Paul was held hostage by Russia (zero).
"I don't suggest he cares now any more than he did then (zero)."
Agencies contributed to this report