Alliance by Marriage

If you and target player both own at least one commander with partner, you and that player
may mutually decide to each exile all your commanders except one with partner (commanders exiled this way may not be sent to the command zone). If they do, these two players shall become one player, who controls the permanents of both and whose life total starts as their average. Hands and graveyards are merged. Shuffle the libraries together and then exile the top half, rounding down.