We know that sulli and heechul are very close but do we know that they are godbrother and sister? Indeed, they are! It was revealed on radio star where f(x) appeared as guest when heechul suddenly appeared at the recording studio.
Heechul said if anyone bothers sulli, he must be the first to know. Such a sweet godbrother right? I believe anyone would be happy enough to be close to heechul because of his crazyness and him being so comedic everytime.
Check out the video! Its eng-subbed!