So I have a player who wants to run a set of twins but use one character sheet for when they fight together, however when they split their ability scores down the middle. I've never had this kind of request come my way...any suggestions?
There are no rules against playing multiple characters but each character needs there own sheet. So just have him make 2 identical character sheets for the twins.
If you want you can give them a minor bonus when there together like a +1 to all rolls or something.
Note that an extra in game character will slow the game about as much as having another player.