The term Familiennachzug (family reunion) is used to describe the right to bring loved ones family to Germany if one is already resident in the country.
When there are Europe (EU) citizens working in Germany they can bring their family, including partners, children aged under 21, parents and grandparents. Provided that they are financially secured and can arrange enough living space. The right to bring along family members also applies to family members who are not citizens of an EU state. They do not require a work permit to take up employment.
Non-EU citizens with a (temporary or permanent) residence permit, family members normally include children under the age of 18, partners and in some cases other family members. Only after certain conditions have been met, such as the size of the accommodation, the ability of the resident person to support dependents and a basic knowledge of German the family reunion (Familiennachzug) can occur.
Some notes on marriages
If the partner already living in Germany has a valid residence permit, they have the right to come to Germany (Aufenthaltserlaubnis). If the partner living in Germany has a temporary or permanent residence permit (Aufenthaltserlaubnis), then it can only claim the right of Familiennachzug (family reunion), if the marriage took place before the person gained the residency and this was stated at the time of application. People involved have to be 18 years or older.
As long as the marriage was in place for two years after moving to Germany, residency rights are granted even if the partnership has ended. If a couple divorced before two years has expired, individual residency rights are only granted in special cases.
Visits from friends and family
If friends or family members from abroad wish to visit you Germany, this is not governed by the same arrangement ruling family members who wish to remain in Germany. Even if they only want to stay briefly in Germany visitors need to get a visa before coming. Family ties are often taken into account and close relatives are often granted visas, since German diplomatic missions have a considerable amount of leeway when allocating visas.
Your visitor must prove that s/he has means at their disposal to finance their stay in Germany, in order to gain a visa. You will generally need to sign a form at the local immigration office guaranteeing that you will cover the living costs of your visitor if necessary (Verpflichtungserklärung), to prove it.
For processing this application the immigration office often charges a fee.