Welcome to the Wefugees community and thank you for your question.
It is possible for acknowledged refugees to reunite with their core family through family reunification. However, it's limited to spouses and their (underage) children. Children younger than 18 years have a right to get reunited with their parents, but it doesn't include siblings. Brothers and sisters could come after the parents got a residence permit. But since you are 21 already it's not going to be possible to bring your parents to Germany unfortunately.
It is possible for Ausländerbehörde to make an excemption if you can provide convincing reasons why it's necessary to bring your family to Germany (e.g. because your parents are too old so that you have to take care of them). But that's a discretionary decision for Ausländerbehörde - they can refuse.
If you can, you should consult a counselling center or a lawyer that can take a closer look at your case. Maybe they have another idea.
(German language): https://www.berlin.de/willkommenszentrum/familie/nachzug-von-familienangehoerigen/