I am guessing there is more than 1 keyblade but only 1 person who can truly unlock its potintial. that potintial is the wielding of the 2 keyblades.

Riku has one because his was not a real keyblade that can unlock and lock the worlds all his does is unlock a heart

king Mickey has one because he found one inside kingdom hearts

and kairi Do you see her in this one. Or at least with sora .