Russia has a growing problem in Ukraine with Ukrainians in Russia controlled territory supporting and often joining the partisan forces. Many Ukrainians there prefer to move, at least temporarily, to Ukrainian territory. There it is safer and y0u can join the Ukrainian military or leave the country. Russia blocks this and comes up with mostly unsuccessful ways to prevent the increasingly troublesome Ukrainians Russia getting out of Russian-controlled territory. Russia has long handled this problem by moving troublesome civilians to remote parts of Russia. For a long time, this meant exile in Siberia. It’s expensive to move a lot of troublesome civilians to Siberia and in the age of the Internet it often doesn't work as well as it once did.
The Russians have come up with a new oppression technique of taking about a thousand Ukrainian children and finding Russian couples that will adopt them. A small fee is paid to the adoptive families. This violates international agreements and is, in fact, a war crime. It wouldn’t be the first such violation by the Russians in Ukraine.
This is in addition to forcing hundreds of thousands (perhaps millions) of Ukrainian civilians, many of them children, in Russian-occupied Ukraine into camps and controlled-localities all over Russia’s vast territory, generally areas far less pleasant than Ukraine. Russia has done so to troublesome minorities for the past several hundred years.
What is most unusual about this use of children as hostages to pacify occupied regions is that it is happening in Donbas, which has been under Russian control since 2014 and initially supplied troops for he 2022 invasion. As that invasion went bad and got a lot of the Russian soldiers killed or wounded, the surviving volunteers from Donbas refused to fight any longer. Worse, internal security forces in Donbas, recruited from Donbas citizens, quit, because Russia was demanding harsher measures against Donbas residents expressing animosity towards Russian control of the area. Now Russia is bringing in security personnel from Russia to police Donbas.
Most other Russian efforts to diminish Ukrainian resistance in occupied territories are equally dubious when it comes to international law, During the 1930s Joseph Stalin used children as hostages, to assure loyalty and good behavior by subordinates and potential opponents. In the kinder and gentler 21st century, the child hostages are used to persuade parents to behave while under Russian rule. That is not having the desired effect.