Kimbley always had this strange warmth to his embraces, despite his nature.
That's why, Archer figured, Greed was so hurt when Kimbley had betrayed him. Because he had earned that embrace and he had wanted Kimbley to be his forever. That's why he didn't attack Kimbley on the spot; He wanted him back.
Archer never noticed, but Kimbley had stolen one of the many chips of Greed's skull. Greed was always so cold, his touch only appealing to the skin and nothing deeper. Kimbley hated that but he never wanted to forget. Everyone else was neither warm nor cold. Except for Archer. That's why he went with him; He was warmer than so many. He was so sick of being cold.
Archer couldn't sleep without Kimbley. He just felt so cold, no matter how many blankets he had, no matter how much he could feel himself sweat, he never felt warm. He never realized how much sleep had had been missing till Kimbley got there. Archer would toss and turn and eventually sneak his way into Kimbley's bed. Kimbley never minded though. Little did Archer know, Kimbley had gotten so little sleep when he was with the cold and the blank. With Archer, he could finally sleep.
Archer had always regretted sending Kimbley in first. The rage and depression he felt as the scarred man dropped Kimbley's corpse from the roof of the building broke something deep inside him. The warmth inside him quickly faded into coldness as the battle continued and ended far too quickly.
Even as Archer laid on the operating table, waiting for automail to sooth one pain, sweating frost and never warmth as cold bolts of pain flooded what was left of his body, he swore he could feel some warmth as Kimbley's voice whispered and cried words of love and farewell...