Forced russification of non-russian-national children is one of the definitions of genocide. The reason the ICC issued its arrest warrant against putin and Maria Lvova-Belova on the specific charge of kidnapping Ukrainian children into russia is because they bragged about it on russian state TV (i.e. provided the evidence themselves)
I took it in quotes. The children taken from warzone to move them from the Ukrainian attacks, in most cases with their parents’ consent.
It is a normal practice in warfare, the US did it in Vietnam on a larger scale.