Dear @Dana.M,
Welcome to the Wefugees community and thank you for reaching out to us.
If third country nationals (there are exceptions though) want to visit a country in the Schengen area, they have to apply for a respective visa. In most of the cases, those tourist visa are issued for a period of 90 days and are valid in every member country of the Schengen zone. Your parents need to apply for a visa at the German embassy (or maybe even at an embassy of another EU country - depending on the destination) and provide a number of documents and usually also a proof of financial stability. The exact requirements will be found on the website of the German embassy in the respective country.
Without knowing your and your parents individual situation, it is hardly possible to predict the chance of getting issued the visa. I can unfortunately also not name “a good reason” which might be promising for the whole procedure.
Maybe you can visit a counseling office in order to discuss it further.
In any case, please also don’t hesitate to get back to us.
All the best,
Meike