(NewsNation) — The brother of an American detained in Russia welcomes the news that the House of Representatives has put forward a resolution calling for his release.

Paul Whelan, a Michigan corporate security executive, is serving a 16-year espionage sentence in a remote Russian prison. The retired U.S. Marine was detained in 2018. Whelan and Washington sources deny he spied in Russia.

Despite the House resolution, Paul’s brother, David, is no more optimistic about the future.

“I think, unfortunately, what you see with cases like these is that the longer the hostages are held, the harder it can become to get them free,” David Whelan told NewsNation.

The Biden administration had hoped to secure Whelan’s release during negotiations on a prisoner exchange that eventually freed American basketball player Brittney Griner from a Russian prison last December.

But David realizes there’s only so much President Biden can do.

“At the end of the day, it really is President Putin and the Kremlin who have all the power to let Paul go,” he said.

Analysts have pointed out that Moscow may be using jailed Americans as bargaining chips in soaring U.S.-Russian tensions over the Kremlin’s military operation in Ukraine.

David also said his brother is facing “retaliation” from prison guards after he refused to give an interview to a Russian television station.

“(Paul) has had his possessions stolen, he’s been kicked around by the prison guards, he’s had his ability to phone our parents or phone the U.S. Embassy interfered with on a regular basis,” David said.

And though Paul is the one in a foreign prison, David is also worried about their parents.

“My parents, who are in their 80s, have to live with this every day,” said David. “It’s the anxiety of wondering whether Paul is going to call.”

The Associated Press contributed to this report.