How many is it I thought it was five

Mickey

Riku

Sora

Lea

Kairi

 

So is it these five or is it just mickey?

Probably more than Googol.

He didn't really 'train' anybody that we know of past Mickey. He simply put Sora and Riku through the Mark of Mastery. His training of Lea and Kairi hasn't been seen yet, so it hasn't happened. Mustn't rush the storyline.  

He trained Donald and Goofy I'd assume.

But if a keyblade master puts someone through a mark of mastery test, doesn't that mean they are trained by them to become keyblade master through whatever task the test makes you do?

 

If that makes any sense  

But if a keyblade master puts someone through a mark of mastery test, doesn't that mean they are trained by them to become keyblade master through whatever task the test makes you do?

 

If that makes any sense  

I guess, if you want to grasp for straws. But he didn't REALLY train them. Sora and Riku are self-taught Keyblade wielders, and that test was also them teaching themselves. The only thing Yen Sid gave them was knowledge, not on how to be a Keyblade master, but on the history of light, darkness, the World, etc. He's more of an educator to them than a teacher. (Yes, there is a difference.)

 

The only person we know for a fact that he trained was Mickey. He may have taught Donald and Goofy, but that's never been confirmed. 

Wait sense Sora failed the test and Riku became a master. Does that mean that Sora is going to be Yen Sid's apprentice in KH3?

He didn't really train Sora or Riku, and Kairi and Lea we do not know. Only Mickey.

 

Donald trained under Merlin, and Goofy has no confirmations.

He trained Donald and Goofy I'd assume.

lolwut

Goofy and Donald may have just been trained by Mickey.

Probably more than Googol.

Funny how I was going to say that.

He did train mickey and he might train Kairi and Lea, but the answer will just be only mickey.