"Native speaker" is not a very useful term: it combines a lot of criteria (first acquired language, language you know best, language you identify with, language of your parents, language of your ethnic group etc.), and each of these criteria is further very fuzzy (e.g. I know plant names better in Ukrainian, but programming terms better in Russian, which language I know better? Competency is not a single value, ethnic identification is malleable and people can have several of these, etc.)

These criteria usually coincide in speakers of big languages (usually languages of [former] empires), so it's relatively easy to say who is a native speaker of Russian or English. There are a lot of people who fulfill all the criteria at once.

But they rarely coincide for speakers of smaller languages (usually colonised people). When most people are bilingual, it's often harder to say who is a native speaker of Ukrainian or Belarusian. Most people fulfill some criteria but not all of them.

So, the term "native speaker" is not neutral and not very useful.