Jung Yonghwa, Lee Jonghyun, Kang Minhyuk, and Lee Jungshin known as Brothers of Four at Baekhwa village in Busan. People acknowledge their talent since they were young. They only little boys but have great sense of music which make their face glowing like sun beam whenever they played with their instrument. 

Here's a short story about them.  Go and check it out, guys! ^^