His family says Barnes' arrest came after he traveled from his apartment in The Woodlands, Texas, to Russia at the end of 2021 to try to gain visitation or custody rights to his sons through Moscow's family court system.
Barnes, a 68-year-old father of two boys, is serving the longest prison sentence of any American who is currently being held in Russia. He was recently relocated to a penal colony hundreds of miles from Moscow.
Barnes was convicted by a judge in Moscow in 2024 and sentenced to more than 21 years in prison.
After spending years in a detention center in the Russian capital, Barnes was recently transferred to the IK-17 penal colony, according to a spokesperson for his family. The facility previously housed other high-profile detainees like American Paul Whelan, who was freed from Russia in 2024 as part of a prisoner swap.
Carter and Barnes' siblings have maintained their hope for years that an exchange like the ones involving Whelan, Brittney Griner or Trevor Reed could bring Barnes back.
ABC News' Tanya Stukalova contributed to this report.