Birth by Sleep Keychain/characters theory

Alright this is a Vanitas and Ventus theory in one. We all know that Vsnitas means vanity and mirror, right? So couldn't that mean that Ven and Vantias are 2 halves of one whole? Or perhaps the bonding of two similar keyblades. Perhaps the burial or grave operation as other cultures have done such as the greeks putting a coin under the tongue of a dead person and the burning of the jedi. That leads to this explanation; the burial of a fallen keyblade master is turning them into keychains. We all saw Aqua hold out 3 keychains, correct so that that leads me to believe she can make key chains.
Vanitas might be the inverse kingdom key key chain and Ventus might be the Kingdom Key key chain.

Now how would this explain the connection between Sora and Ventus? Key chains are apart of the users heart, correct? So the transferring of memories might affect the user's heart. This would explain all those keyblades in Sunset Horizons. That would be the burial site. I know it isn't canon but the 3 of them picking up the 3 keyblades might be saying they're coming back to life to fight again

 

Aqua gave out three lucky charms in the shape of Paopou fruit. I believe. That's if you're talking about the trailer. They were given so as to keep the apprentices bonded together, even while they travelled from world to world.

And concerning keychains, i'm gonna guess they aren't integral in the creation of a Keyblade, seeing as some Keyblade wielders are shown to use them without the need of keychains.

There may be a possibility that after someone dies, loses their heart, or whatever, their leftovers could be made into a keychain, that might explain the use of keychains.