Taemin and Kai have been friends for longer than Tae debuting with SHINee. They were even rumored to have auditioned for SM together, hoping to be in the same group, but got split up when Tae was put in SHINee. Even though they aren't in the same group, their friendship is still going strong. The friendship contains mostly, 90% of them teasing each other. When Taemin had long hair, Kai would always joke around and tell others that Tae was his girlfriend.
De heavenlynote - Source 5mars2013