In Germany an identification card is compulsory from the age of 16 years. An identity card applies to all trips inland and to countries of the Schengen Agreement as a valid identity document.
The normal Passport can be applied for regardless of age for children. Some countries require a passport for entry, for example into the USA. The passport must be requested at the local registration office. For persons under 18 years of age, however, the written consent of both parents or a power of attorney of the non-present parent is required.