Actor Kim Won Joon has revealed his special relationship with Lee Hyori. On May 10th, the�KBS radio show 'Ock Joo Hyun's Music Square' had MC Ock Joo Hyun make a surprise phone call to Lee Hyori since it was the latter's birthday that day. Kim Won Joon, who's a permanent feature on the show, said, "I've seen Lee Hyori before I debuted. There was a passionate fan who used to follow me around, and her friend caught my eye because she was pretty; that friend was Lee Hyori." He continued, "After finding out Lee Hyori had a bigger sister, I used to jokingly call her my sister-in-law." Meanwhile, Kim Won Joon is currently busy with his project vocal group, M4. Source: Osen via Daum