That not should be so hard to do. I musted do something like it.
First at all you must check where should be your cam. In order to do that you must check player 1 Location and player 2 Location.
When you have it do this operation:
(Location X Player 1 + Location X Player 2) / number of players = Average Location X
Same for Y and you will have your cam always between them (just update camera location in every tick in your cam event graph).
After this we should try set new rotation, but I guess you will find the way to do it, if not post again
Edit: oh, I forgot something more. In order to keep your players always in screen, you must update too the camera “spring arm” lenght (I guess it was how it called). For this get “Vector lenght” of the current cam location and set “spring arm” lenght with this value.