I was trying out a scarab deck with Gemini and he TU'ed one of my scarabs, then TU'ed the new twin. At the end of his turn, the first twin's hp dropped to 2 (since there were only 2 scarabs on his side) but the other one did not. I devoured the first one but 2 turns later, the second twin retains the swarm bonus hp despite being a loner.
EDIT: This is in the trainer--no idea if it occurs in real game.
