Taken from here.

JYJ Junsu “This Isn’t Right, Hyung” A Message to TVXQ?
Group JYJ member Kim Junsu’s tweet had left fans in agony.

Kim Junsu in the afternoon on January 6th wrote in his twitter, “This can’t be true… I came to believe that the person was the enemy of all five of us, however now I think not all of us see it that way.” “Seeing how you express your gratitude to someone who was our enemy, makes me wondering… there must be a lot of things happened when we were apart for a long time. I’m getting tired.” he wrote.

He continued, “I try to think, see, and listen only to the good things from all these times, but just today I find it really difficult.” Kim Junsu also wrote, “Eventhough we’re apart, this isn’t right, Hyung. We used to share the same thought. Why are you doing this.” the writing seems to concern to a specific person.

JYJ fans had assumed that the tweets were messages for the two members of TVXQ.

At the new album of TVXQ after 2 years and 3 months hiatus, leader U-Know Yunho thanked to SM Entertainment Lee Soo Man at his THANKS TO note. U-Know Yunho said, “TVXQ’s second act is starting now.” The writing is taken as a message to mark the beginning of the new TVXQ.

Prior to Kim Junsu’s tweet, Youngwoong Jaejoong changed his profile to “You keep your head up and keep an open mind” and wrote a meaningful sentence, “I’m just hoping to be. I close my eyes, ears” that drew a lot of attention.

The writing ‘Keep your head up’ is speculated to refer to the song lyrics of TVXQ’s title song ‘Why (Keep Your Head Down)’ that has been put the company SM Entertainment under controversies.

Kiyuuu says, "I mean, it does seem the lyrics are refering to JYJ, whether or not SM says so. Let's keep faith... JYJ, TVXQ hwaiting!"