§ 27 Principles pertaining to the subsequent immigration of dependents
(1) The residence permit to enable foreigners to be joined by foreign dependents so that they can live together as a family (subsequent immigration of dependents) shall be granted and extended to protect marriage and the family in accordance with Article 6 of the Basic Law.
(4) The period of validity of a residence permit for the purpose of the subsequent immigration of dependents must not exceed the period of validity of the residence permit held by the foreigner whom the dependents concerned are joining in the Federal territory. It shall be issued for this period if the foreigner who is to be joined in the Federal territory by the subsequently immigrating dependents holds a residence permit pursuant to Section 20 or Section 38a or an EU Blue Card ….
§ 29 Subsequent immigration of dependents to join a foreigner
(1) For the purposes of subsequent immigration to join a foreigner,
1. the foreigner must possess a settlement permit, EC long-term residence permit, residence permit or an EU Blue Card and
2. sufficient living space must be available.
(5) The residence permit shall entitle the holder to pursue an economic activity,
1. where the foreigner whom the subsequently immigrating dependents are joining is entitled to pursue an economic activity
2. whrer the foreigner to whom the family reunion takes place, has a residence permit according to § § 19a or 20 or
3. where marital cohabitation has lawfully existed in the Federal territory for at least two years and the residence permit of the foreigner whom the subsequently immigrating dependents are joining is not subject to a subsidiary provision pursuant to Section 8 (2) or extension of his or her residence is not excluded by law or by an ordinance.