REGISTER TO REMOVE ADS
Uh, really, all we saw was Mickey summoning a Keyblade, placing it on a table, and then walking away dejected. Yen Sid then puts it back into Mickey's hands.
It doesn't REALLY show that Yen Sid is a Keyblade Master...
The Star Seeker is Mickey's Keyblade - all we know that Yen Sid is a powerful sorceror (Fantasia).
Aside from Mickey, there are no known characters from Disney OR Final Fantasy that have or can possess a Keyblade.