Dorii and Guraa are twin archers serving under Oboro. They are talented archers and often lead archer groups in Hakuoro's army.
There are few ways to tell them apart. For one, Dorii has purple eyes while Guraa's are blue. Also, the bottom part of Dorii's clothes are blue while with Guraa they are red. You really can't make them separate characters since they're always side by side. They are somewhat androgynous, and as such their gender is difficult to ascertain, even by other characters.
In the game, they reveal they are male, in the anime their gender isn't revealed.