VORONIUK and NAHORNY are old Ukrainian surnames !!!
From late 18th century to 1921 the large Vohlynskaya gubernia/region
belonged to the Russian Empire. From 1921 - 1939 the Wohlynskie
wojiwodstwo/region was under Reconstituted Poland's domain.
TECHNICALLY POLAND HAD NOT EXISTED AS A GEOPOLITICAL ENTITY
FOR THE PREVIOUS 125 YEARS. After World War 2, Vohlyn became a
part of S.S.R. Ukraine, under Soviet domain, until 1991 when Ukraine
became independent. (During the Soviet Period, Vohlyn was divided
into smaller regions: Vohlynska oblast, Rivnenska oblast, small piece
went to Belarus, and Zhytomyrska oblast. Additional a small part of
Ternopil, which during Interwar Period was part of Wohlyn, was returned
to the Ternopilska oblast.)
Your Grandparents were ethnically Vohlynian Ukrainians. Given their
birth years they were born Polish citizens. Just like the Halyczany, who
emigrated from Galicia/Halyczyna Province > Austro-Hungarian Empire,
were ethnically Ruthenian/Ukrainian, but technically Austrian citizens.
"Just because a kitten is born in a barn, does that make the kitten a cow?"
Try real hard to remember exactly where your Grandparents were born.
.