Holders of the Blue Card EU in Germany have the option of obtaining an unlimited national residence permit (settlement permit) after 33 months of highly qualified employment and simultaneous payment of contributions to a pension scheme.
If the holder of the Blue Card EU has sufficient knowledge of the German language (level B1), he can already apply for a settlement permit after 21 months.
Anyone who has had an EU Blue Card for at least 18 months of another EU member state may enter another member state without a visa and apply for a Blue Card EU of this member state within one month. In addition, holders of an EU Blue Card can stay in non-EU countries for up to twelve consecutive months without their residence permit expiring. The rules on facilitated mobility also apply to family members.
For the family members, there are also other attractive aspects of the EU Blue Card. Spouses are entitled to a residence permit, even if they cannot show any knowledge of the German language (§ 30 Abs. 1 Satz 1 Nr. 3g and Satz 3 Nr. 5 AufenthG).
Spouses also receive immediate unrestricted access to employment and self-employment (§ 27 (5) Residence Act).
Source: https://www.bamf.de