Looking for info on Rusnack/Rusnazzk

I was wondering if anyone might be able to provide information on the aforementioned surnames. My family's name is Rusnack, and I was able to find my great-grandfather, Jacob John Rusnazzk, had come from Poland in 1904 with his parents, and the name was eventually "Americanized". I spent several days combing through information on Ancestry.com but only found siblings on Jacob. They didn't even have all of them, because my grandfather told me of two that weren't shown!

Anyway, I've been searching for a long time, and haven't been able to find any information, so any help would be appreciated.

RUSNAK/RUŚNIAK: These are the most probable Polish spellings both of which exist as surnames. This is a nationality-derived surname identifying someone as a Rusniak, a Ukrainian ethnic subgroup which includes Lemkos.