Dynamic Split Camera with Perspective Camera

Hi, I am trying to implement a dynamic camera game, There are two character in the scene, when they are close to each other, they are both displayed on the same camera, When their distance above some value, I use another two cameras to display them. Cause we wanna the split screen in this situation.

The problem is over here, When I turn off the main camera and turn on another two cameras, The background is not connected, some background will overlap in both camera. Then I tried another way, I rotate the angle of camera and everything is not strait anymore.

Does any one know how to use perspective camera implement dynamic split camera? I've tried to implement it on Orthographic and it work good(Cause z value doesn't matter anymore), but I really want to do it by perspective camera. Please.