Luhan is one of the oldest members and Sehun is maknae but they look like twin.
Just looking at their picture can make you become HunHan shipper :).
Have you ever confuse which member Sehun with on "What is love" MV?
It seem 2 Sehun right?
Ah~, pause at this, this is Luhan, and Sehun...
picture from SM's What is love MV and SM's facebook