To be allowed to stay in Germany for as long as you want to, you need to get something that is called a settlement permit. With a settlement permit, one can stay, work and travel in-out of the country whenever they need. In order to get this permit, you should be holding the temporary permit i.e. the EU blue card for a couple of years, you have to prove to the Federal Employment Agency that you have worked for at least the past five years and that you have paid the necessary taxes to the government. And last but not the least, you gotta show your German language proficiency. Plus, your children and spouse are allowed to join you when you get a permanent residence permit. They would have to get the EU Blue card at first and after a few years, they'll be able to get the permanent permit.
Documents that you'll need are:
