Siwon's instagram name is: siwon1987

Siwon was actually born on April 7, 1986 BUT was registered under February 10, 1987

Sooyoung's birthday is February 10, 1990

This means one of two things!!!

1) Siwon likes his 1987 birthday more because he shares it with Sooyoung!!!!!!!!!

OR

2) 'siwon1986' was taken...

I like my first reason better!!!