Mother tongue, first language or native speaker?

Today you get another post about languages, this has always been a topic that has frustrated me so much because I speak English as a first language yet many people will not consider me a native speaker because of the colour of my skin. I also talk about my mother tongue and my heritage language, which I am not fluent in. Yet many people will not even question me if I claimed to be a native speaker of that language. There’s something incredibly wrong with the way most people classify native speakers.