This is stupid. haven't any of you hosted server where people log in and then log in again? They have no clue what the other "them" is, it's just a glitch. The other them usually just doesn't move. The connection is a bit laggy and insufficient sometimes which can cause weird errors. If I boot one of em, the one I boot is NEVER the one playing. The computer basically "chooses" the player who isn't connecting.
If this other you doesn't speak, type, or otherwise I wouldn't worry about it.