Wheesung once mentioned about his closest & favourite hoobae in an interview on a radio show.
The person is none other than SHINee's Jonghyun.
They have their ways of being close to each other by their "jokes" that they both understood.
They are really close to each other.
In a recent interview with Wheesung, he once again mentioned about SHINee's Jonghyun.

* This is only the Jonghyun-related portions of the article

It’s just the title song, not personal experience. Insomnia·depression… Now I can laugh. The one who turned me good-natured is SHINee Kim Jonghyun.

Wheesung boasted that he achieved the greatest desired result during album promotions in transforming ‘unpleasant’ to ‘pleasant.’ He named idol group SHINee’s Kim Jonghyun as being the most help in that transformation.

“These days I’m greeted and welcomed warmly wherever I go. This is all thanks to Jonghyunie. Because I gave Jonghyunie pointer lessons when his throat hurt and I participated in SHINee’s album as a lyricist for 2 songs, their fans even support me.”

Source: dongA

Original article: http://news.donga.com/3//20100928/31437042/1

English translation: live laugh love @ soompi