Wow are my eyes playing tricks on me?! There are like two Onew! haha
Sadly, he is not Onew's twin but actor Kwon Jae Young from 'A Bit of Love'. The two posed a photo together after the filming of the sitcom, in which Onew will appear as Lee Won Geun's (Jae Young's character) cousin.
It would be so much better if there were actually two Onew in this world, so we fangirls don't have to fight so hard over him lol. But they do look alike a lot! Anyway, you can see them together in the episode aired on May 10th.