evidence: However, in cases where the parents are married, but do not have the same married name, the parents will have to make a name declaration in order for the child to obtain a birth name, even if the child has already been registered abroad under a certain last name. [...] A double last name combining the parents’ last names is usually not possible according to German law. In cases where one parent has a citizenship other than German (e.g. U.S. citizenship), the parents have the possibility to choose foreign law to become applicable for the child’s last name. The last name of the child will then be governed by the law of that parent’s nationality, so a double name (or indeed any other combination) may be possible if that law permits it. The name selection does not apply to future children. [...] - passports of both parents; for non-U.S. citizens residence permit (visa or Green Card)