This is an un-documented situation in last pocket 8 ball and is usually one that should be clarified before starting the game.
@Typeaux is correct in his previous answer, and mine just builds on what he said.
You generally can not have the same last pocket as your opponent. If your opponent ends up with the same last pocket as you, there are several variations of rules you might encounter for assigning the 2nd player a different pocket:
- The first player gets to choose which pocket is the opponent's last pocket (with the following caveats):
- If players have the same side pocket, the 2nd player to pocket their last ball is automatically assigned the opposite side pocket.
- If players have the same corner pocket, the 1st player to pocket their last ball in that pocket assigns the other player any one of the other three corner pockets.
- Same as above, but without any caveats. The first player to own the contested pocket may choose any other pocket for the opponent, including side pockets.
- The 2nd player's last pocket is chosen automatically if his last ball goes in his opponent's last pocket.
- If the original pocket is a side pocket, the opponent is automatically assigned the opposite side pocket.
- If the original pocket is a corner pocket, the opponent is automatically assigned the diagonally-opposite pocket.
Once the 2nd player's pocket has been designated, he may continue his inning at the table.
I've added these to the main article on last pocket 8 ball.
Here are four different folks confirming this from various other 8-ball forums:
A few folks confirming this to be a "generally known" standard part of the last-pocket eight ball rules:
One rule that we also liked was that both players could not have the same last pocket.
That is a standard Last Pocket rule, in my experience. If you take the same last pocket as the first established player, said player gets to pick your last pocket.
And two more players confirming it in a different thread (but in this case, the player choosing the pocket for the other player is allowed to designate side pockets as well):
In Puerto Rico, if you pocket the last ball in your opponent's pocket, your opponent can nominate your pocket, including side pockets.
I've always played that the opponent gets to pick the shooter's last pocket (if the shooter makes their last ball in the opponent's last pocket)... even choosing the side pocket. I've also seen it played where the shooter's pocket, in this circumstance, became the opposite pocket (on the other end of the table).