Kwangmin likes Minwoo, who likes Youngmin, who likes Donghyun, who likes Kwangmin.  Those 4 members are busy with their own love quadrangle so it only makes sense that Hyunseong and Jeongmin were always left alone together.

Everybody seems to like Youngmin and that's how Kwangmin ended up in a pretentious relationship with Jeongmin.