Worldwide, Kostiuk (Kostiuk , Костюк ) is an extremely rare gender-neutral first name. Much more frequently, Kostiuk is the last name as well as the forename.
Kostjuk, Kostyuk, Kosťuk, Касцюк, Костиук, Костйук, and Косьтюк
Mr, Tom, Jim, Joe, Jay, Jan, Lia, D T, D E, Don, Dan, R W, Ron, Ray, Ted, Kym, Ken, Bob, A J, Awa, Ann, Ana, Stu, Sam, Mel, Ed, Jd, Al, Ms, Kim, and Tim
, Костюк 
) is an extremely rare gender-neutral first name. Much more frequently, Kostiuk is the last name as well as the forename.