That's like saying isn't the world made up mostly of Africans? Since it's said that we're all descended from individuals that lived in Africa before anywhere else.

So yeah, as the other poster mentioned, "if you go back far enough". If you go back far enough, we're all relatives, too. But that doesn't necessarily have meaning by itself. It's the individuals that choose to, or choose not to, apply meaning from such a technicality.