Many European countries adopt some form of jus sanguinis (right of blood) or jus soli (right of soil) law (or a combination of both). In countries that recognize right of blood, such as Germany and Ireland, citizenship is attainable through parental descent, and possibly even maternal grandparents. Jus soli countries, such as France, may grant citizenship to those born in the country under special circumstances, regardless of ethnic or cultural origin. The processes used to attain citizenship through right of blood or right of birth (or both) heavily vary between EU member states.
Article source: http://www.huffingtonpost.co.uk/adam-manuel/four-ways-to-retain-eu-ci_b_13122914.html?utm_hp_ref=uk-politics&ir=UK+Politics