Apparently, Yoo Seung Ho and f(x)'s Sulli have been friends since they were young children.
The above photo was recently shared on an online community board under the title, "Sulli and Seungho oppa.. Who knew these little kids would become top stars?".
The two had posed together while they were child actors. Yoo Seung Ho had thrown his arm around Sulli, and they were smiling brightly at the camera. Both of them look just as they do now, merely a decade or so younger.