All over the world, Kostyev (Kostyev , Костьев ) is an extremely rare unknown gender first name. Much more prevalently, Kostyev is the last name as well as the forename.
Костев, Костиев, Костыев, and Костєв
Mr, Viktor, and Alexander
, Костьев 
) is an extremely rare unknown gender first name. Much more prevalently, Kostyev is the last name as well as the forename.