During the 'Star Golden Bell' special on August 24, Kai talked about his trainee days and revealed, "I was born earlier in the year so I went to school earlier than most kids my age. I was in the same grade as Taemin so I suggested we be friends but he said he's the hyung."
Kai was born in January of 1994 while Taemin was born in July of 1993.
To this, Taemin explained, "At the time, it was decided that we go by the year we were born." He continued, "Kai ended up dropping the honorifics anyway."