Are Terra, Aqua & Ven's keyblades real keyblades?

i believe that if a keyblade has a keychains then other wielders can use it. If a Keyblade has no keychain, then it is only exclusive only to its wielder, and cannot be given to another Chosen Keyblade Wielder

i think, maybe because it dosent have a chain on the bottom of thre keyblade.

My personal theory is that they are artificial Keyblades. You know there are Pureblood Heartless and Emblem Heartless? Emblem are MADE by man. Pureblood are those stripped of their hearts naturally. I think Terra, Aqua, and Ven's Keyblades are made by them or their master (if they have one). See?

i suppose they ARE real keyblades, just those particular three aren't real masters

every keyblade has to have the keychain

Yes here keyblade bender or masters

Aqua is the only keyblade master of the three because both terra and ven are deemed unworthy to pass the test this is most likely why their keyblades lack keychain or i could possibly mean these keyblade donot belong to a realm or certain world which is why when not in use they don't dissapear.
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I believe that the key chain actualy are on world given keyblades. If you notice all keyblades known befor Birth By Sleep had been given. Kingdom Key or rather the keyblade of the realm of light chose Sora, likewise the kings key was given to him by the realm of darkness and all others come from chains from different worlds. however this isn't the first showing of keys with no chains. Soul Eater was born of Riku's heart and had no chain but gained a chain in castle oblivion and became Way to Dawn. so with this in mind the three keys from Birth By Sleep may have been born directly from their hearts. and also Terra's key does get a chain when it goes from Earthshaker to Ends of the Earth in the key blade graveyard.

yus. probs it is.... i think