While filming for the upcoming episode of MBC's 'Four Guys One Girl,' Kim Woo Bin revealed that he turned down an offer to appear on 'Radio Star' because of Kim Gu Ra.

He said, "I'll be honest.  I was asked to appear on 'Radio Star' to promote a movie, but I gave up the spot because of Kim Gu Ra," which took Kim Gu Ra by surprise.  

Kim Woo Bin continued, "Kim Gu Ra was a bit scary.  However, now that I've met him today, I feel a somewhat special warmth from him."

SEE ALSO: Kim Woo Bin holds his first fan meeting in 5 years

On the show, Kim Gu Ra may have grumbled a bit, but he took very good care of Kim Woo Bin and was supposedly unable to hide his happiness at the fact that Kim Woo Bin became the youngest sibling.

You can watch their growing sibling relationship when the episode airs on April 4 at 10 PM KST.