Ok, your grandfather was Jakob Dworatschek, b. 27 Jun 1897. He was the son of Jakob Dworatschek who was born in 1871 in Kernie.
The names and birth dates of your grandfather's siblings is the only information in the Kernei Familenbuch about the family. Perhaps you already have that information? If not, I can give it to you.
You might want to check Ellis Island records to see if any of them immigrated to the U.S. If so, you can then check U.S. census records for them. Census records are available every 10 years through 1940. Once you do that, there are other records that can be checked. I'd be happy to help you if you determine that they immigrated to the U.S.
Since your great grandfather was my great grandfather's brother, we are third cousins. My grandparents and father immigrated in 1920 and settled in Chicago.