In the entire world, Касцюк (Касцюк , Kastsiuk ) is an extremely rare unknown gender first name. Much more frequently, Касцюк is the last name as well as the forename.
Kostiuk, Kostjuk, Kostyuk, Kosťuk, and Костюк
, Kastsiuk 
) is an extremely rare unknown gender first name. Much more frequently, Касцюк is the last name as well as the forename.