I just had an idea if we assume that all these champions are Darkin 
and
what if
is war
is conquest
and is death
then we have all the known Darkin right and we are only missing Famine. So what do you think Famine should be? A new champ or a old one?
Kindred is death. Neither of them are Darkin.
There's five Darkin left in existence, not four, so there'll be one left over in this theory.
There's nothing stated about Jax wanting to conquer anything. He just likes to fight and has a good time doing it.
I'm seeing a lot of holes in your theory good sir/madame/however you identify, and while I praise your efforts I have to say that this theory doesn't have a lot of ground to stand on.
None of those champions is a Horsemen... In fact, i bet that Jax has never seen a Horse in his life.
Checkmate atheist
Kindred is definetly not a darkin and I doubt that jax is one.
In the end it is possible that the 5 darkins are going to represent the horsemen of the apocalypse(sometimes conquest is replaced with pestilence,so they could make 4 based on the original horsemen and one more for pestilence). But honestly there is currently not much information about the darkin as a whole,so the only basis for that would be that aatrox is a dude who likes war.
