Complex sentence: Generally, the nations in these areas of the world follow the principle of jus sanguinis rather than jus soli in order to determine one's citizenship, but even then most of these countries determine one's nationality by their ethnicity, rather than citizenship.
Split into simpler sentences: Generally, the nations in these areas of the world follow the principle of jus sanguinis rather than jus soli. And even determine one's nationality by their ethnicity, rather than citizenship.