The two Brothers could be controlled by different players.
There are two versions of this card, each with different art. The cards are numbered 160a/306 and 160b/306. The art has no effect on game play.
If a third Brothers Yamazaki enters the battlefield, the legend rule will apply. If one player controls more than one Brothers Yamazaki at that time, that player will have choose one and put the rest into their graveyard.