The children of a Russian spy couple, who returned home on Thursday following the largest prisoner swap between the West and Russia since the Cold War, only learned of their nationality during the flight to Moscow.

Artem Viktorovich Dultsev and Anna Valerevna Dultseva had been posing as an Argentine couple living in Slovenia when they were imprisoned there. Their children, who did not speak any Russian and were unaware of President Vladimir Putin, asked their parents who he was when they arrived, according to Kremlin spokesman Dmitry Peskov.

The exchange involved 24 people jailed in seven different countries. Sixteen were Western prisoners detained in Russian jails, and eight were Russian prisoners held in the US, Norway, Germany, Poland, and Slovenia. Among those exchanged was Wall Street Journal reporter Evan Gershkovich.

The Russian family of four received a warm welcome, with Mrs. Dultseva and her daughter being greeted with flowers and an embrace from President Putin. The president greeted the children in Spanish, saying “Buenas noches.”

Argentinian media reported that the couple, known as María Mayer and Ludwig Gisch, had arrived in Slovenia with Argentinian passports in 2017. Mr. Dultsev set up a start-up IT company, while Mrs. Dultseva ran an online art gallery. They used Ljubljana as their base until their arrest by Slovenian police on espionage charges in 2022.

Ahead of the large-scale prisoner swap, Mr. Dultsev and Mrs. Dultseva were each sentenced to 19 months in prison after pleading guilty to spying charges on Wednesday. However, considering their arrests in 2022, they were released on time served and ordered to leave Slovenia, as reported by the Associated Press.

During the prisoner swap on Thursday, the Kremlin spies and their children were returned to Russia. The lives of 11-year-old Sofia and 8-year-old Gabriel, who were born in Argentina, changed dramatically as they learned they were Russian only when their plane set off from Ankara to Vnukovo Airport, according to the Kremlin.