That's... not quite how Dual Wielding works. People who have two keys have them because the second blade they possess used to belong to someone else whose Heart is now shared with theirs. It's how Roxas wielded two blades (made up of both Sora and Ventus' hearts), and Sora's drive forms combined his Heart with Donald or Goofy's to achieve dual wielding.

There's also this snippet from the OP post:

[quote]Heart of the Valorous: Those with this heart carry two keyblades, making them experts in fighting other keyblade wielders and heartless. However, because of these twin blades they lack defensive ability and cannot move as quickly. Their is no shared trait however, [b]each of these wielders carries heart of another in their own heart.[/b][/quote]