A situation with the germanic ascendence

Hello! Nice to meet you all,

I'm new at this forum. Thanks you for reading.

My great grand parent was German, probably a refugee after WWII, as my grandma told me. The thing is, my grandma really does not have her birth certificate sign up by him and he was always very far from his family, so we really don't know much about him. We only have his name. Not even the place or the city he was born.

Now, my question is, Is there, by any chance, a way where I can optain a german passport by ascendence? I know it sounds kind of stupid. I've though that It is, indeed, imposible. But I found this forum and had to ask.

Still, thanks you so much for your time.