>this is the very opposite of the ideological premise to justify a genocide.

Genocide is an attempt to kill a group; That does not happen only by murdering people - it's also forced assimilation. In this case, Russia is directly violating article 2) e) of the Genocide Convention*: "Forcibly transferring children of the group to another group."

>citizenship

Citizenship is not relevant to the genocide convention at all.

* https://en.wikipedia.org/wiki/Genocide_Convention