Is this surname polish, Lithuanian or Belarusian?

[Sikeliot]

Greska

Assuming this is the original spelling.

[Bobby Martnen]

It sorta reminds me of Gretzky, whose father described the family's heritage variably as Polish, Russian, Belorussian, and Ukrainian.

[Sandman]

This is a very rare surname in Poland. There are only 7 people with this surname in Poland.

http://www.moikrewni.pl/mapa/kompletny/greska.html

[Sikeliot]

This is my great great grandmothers surname. She was born in Poland to the best of my knowledge but I've never heard of the surname.

[Bobby Martnen]

This is my great great grandmothers surname. She was born in Poland to the best of my knowledge but I've never heard of the surname.

Try to get a male-line descendant of the lineage to take a Y-DNA test. If it's R1a, she's probably Polish. If it's N1, she's probably Lithuanian.

[Sikeliot]

This is a very rare surname in Poland. There are only 7 people with this surname in Poland.

http://www.moikrewni.pl/mapa/kompletny/greska.html

My great great grandma was special then!