Basically, the principle of descent applies. According to this, the nationality of the child is determined by the nationality of the parents. The child receives the nationality of the mother or his parents at birth.
If only the father has German nationality and is not married to the mother, valid recognition or confirmation of paternity under German law is required. Such a procedure must be initiated before the child reaches the age of 23.
A child of a foreign parents born in Germany receives German citizenship at birth if at least one parent has been habitually resident in Germany for eight years and has a permanent right of residence (birthplace principle). Often the child also acquires the nationality of the country from which the mother or parents come from. It then has several nationalities.
It can keep this nationality beside the German if
• they are nationals of EU or Swiss Member States, or
• The child grew up in Germany. That is the case if the child until the 21st birthday
> lived in Germany for at least eight years or
> attended a school in Germany for at least six years or
> has obtained a school degree or a professional qualification in Germany or
> has comparable ties to Germany and the option obligation would mean a special hardship.
If the child did not grow up in Germany, the option obligation arises. The young adult must then decide after the twenty-first birthday whether he or she wishes to retain German or foreign nationality.