How can I make more than 4 player controllers

Hello I am trying to add in keyboard support for my game gameplay wise its implemented but it has messed up a couple things. The game supports 4 players so by adding in keyboard support automatically player controller 0 gets controlled by the keyboard, the problem is, is that means that if I wanted to play 4 players one player has to use the keyboard and one of the controllers just wont work so I need a way where I can have 5 player controllers. The games logic would be able to use that information to fill out which controllers are playing and stuff. at the moment when I try and use create player it works up until player controller ID 3 everything after that just equals -1

I am also curious as to the possibility of having more than 4 controllers connected/plugged in at the same time, I hope there is more insight to this.