Split screen only for specific player

Hi everyone,

My goal is the following:

We have a group of characters (some of them are local players) sharing a same camera.
When one or more players (and eventually some AI controlled characters) are in a group that gets far enough from the main party, this sub-party gets its own camera and the screen is split accordingly.

My question is then, how can I toggle the split screen accordingly? Because, I don’t need the split-screen to only be “on for every players” or “off for every players”, since the parties do not mandatorily represent each players (some parties can get 1 or more players in).

I thought about two solutions:

Split the screen only for specific players (the “leader” of the parties).
Problem : I did not find how to split or unsplit the screen only for a specific player.

Use an actor representing a party and controlled by “proxy players” who will toggle the split screen when added or removed, and which can propagate their inputs to the right character according to which device was used for the input.
Problem: I did not find how to discriminate the inputs given to an actor according to which input device was used.

If anyone has suggestions about how to implement my goal, following those ideas or not, it would be really appreciated.

Thanks in advance.