I wrote this up to provide a list of all the characters, where they come from, and who they are associated with. I'll update it with time, and I encourage anybody reading and finding mistakes/missing connections to please post so I can fix them right away.

I used all the lore I could think of, which was all the champion summaries, the 5 judgments, and the 4 Journal of Justice's that have been released so far. The characters that are associated with each other don't have reasons given, but they can be anywhere from enemies to friends to lovers and whatever else you can think of. Anyways, here it is:

Format:

Champion - Homeland - Associations

Akali - Ionian Isles - Shen, Kennen
Alistar - Great Barrier -
Amumu - Shurima Desert -
Anivia - Unknown > The Freljord - Nunu, Ashe, Tryndamere
Annie - Voodoo Lands -
Ashe - The Freljord - Tryndamere, Anivia, Nunu
Blitzcrank - Zaun - Singed
Cho'Gath - The Void (Icathia?) - Kassadin, Kog'Maw, Malzahar
Corki - Piltover - Heimerdinger
Dr. Mundo - Zaun - Warwick, Singed
Evelynn - Unknown - Twisted Fate
Ezreal - Piltover -
Fiddlesticks - Unknown -
Galio - Demacia - Poppy
Gangplank - Bilgewater - Miss Fortune
Garen - Demacia - Urgot, Katarina, Kayle
Gragas - Great Barrier - Jax
Heimerdinger - Piltover - Corki
Janna - Zaun -
Jax - Unknown - Gragas, Urf
Karthus - Howling Marsh -
Kassadin - The Void - Cho'Gath, Kog'Maw, Malzahar
Katarina - Noxus - Garen, Sion
Kayle - Unknown - Morgana, Garen
Kennen - Bandle City - Shen, Akali
Kog'Maw - Icathia - Malzahar, Cho'Gath, Kassadin
Malphite - The Monolith -
Malzahar - Shurima Desert/Icathia - Kog'Maw, Cho'Gath, Kassadin
Master Yi - Ionia - Singed
Miss Fortune - Blue Flame Islands - Gangplank
Mordekaiser - Shadow Isles -
Morgana - Unknown - Kayle
Nasus - Unknown -
Nidalee - Kumungu Jungle -
Nunu - The Freljord - Anivia, Ashe, Tryndamere
Olaf - Lockfar -
Pantheon - Mount Gargantuan -
Poppy - Bandle City (?) - Galio
Rammus - Plague Lands -
Ryze - Unknown -
Shaco - Unknown -
Shen - Unknown - Akali, Kennen
Singed - Zaun - Warwick, Blitzcrank, Master Yi, Mundo
Sion - Noxus - Katarina, Urgot
Sivir - Noxus -
Sona - Demacia -
Soraka - Ionia - Warwick
Taric - Unknown -
Teemo - Bandle City -
Tristana - Bandle City -
Tryndamere - Nomadic > The Freljord - Ashe, Nunu, Anivia
Twisted Fate - Demacia - Evelynn
Twitch - Zaun -
Udyr - Ionia -
Urgot - Noxus - Garen, Sion
Veigar - Bandle City -
Vladimir - Noxus -
Warwick - Zaun - Singed, Soraka, Urf, Mundo
Xin Zhao - Demacia -
Zilean - Urtistan -

So, as all this shows, if all is correct, it means there are this many per category:

Ionia: 4
Great Barrier: 2
Shurima Desert: 1/2 (depending on how you count Malzahar)
Icathia/Void: 3/4 (depending on how you count Malzahar)
Zaun: 6
Noxus: 5
Demacia: 5
The Freljord: 2 (4 now that Anivia and Tryndamere have joined the city-state)
Voodoo Lands: 1
Piltover: 3
Bandle City: 5
Bilgewater/Islands: 2
Howling Marsh: 1
The Monolith: 1
Shadow Isles: 1
Kumungu Jungle: 1
Lockfar: 1
Mount Gargantuan: 1
Plague Lands: 1
Nomadic (roaming): 1
Urtistan: 1
Unknown: 11

Assuming of course my math is correct
Anyways, I'll end this post here since it's getting wayy too long. Feel free to comment and correct anything I posted, and I'll definitely be keeping this post up to date with new champions, journals, and any other lore updates.
Thanks for reading

Heimer says "the existence of twitch proves anything is possible in runeterra" so thats kind of implies he knows twitch

Anivia originally came from an "icy world" and then moved to the Northern ironspike Mountains and is assosciated with Nunu and Ashe

And i think Soraka is assosciated with yi, btw nice thread.

Would you think that Alistar could have ties with Xin Xao. Were'nt they both noxian gladitorial fighters? just putting that out there.

Wanted to make similar thread myself, but on diffrent point. In recent Journals of Justice there was talk about Trynd Joining forces with Ashe, anti-yordle movements in Nosus and such, and it all seems like trying to pin every champion to faction and separate them.
Since you've phrased it "orgin" it's a bit diffrent. Tryndamere has nomadic orgin but currently he's on the same side as Ashe/Nunu/Anivia

And if we're talking about sides, there is probably another side, simply League. Fiddlestick is locked in one of League buildings, Jax just like to fight, Olaf wan't to return home, they don't have any special feelings about Noxus/Demacia/other.

Would be interesting to see game mode based on lore, at least in "faction wars"

YAY for Piltover! =D

i'd so live there lol

@ Seasonal: I'm still not sure if that implies a connection between the two for sure, though. I appreciate the comment though, things like that are what I want to hear

@ Valiet: I can't remember if Alistar was a Noxian gladiator but I'm pretty sure he was something like a gladiator. Still, that doesn't give him a for sure connection to Xin.

@Raele: I wasn't aware Nunu and Anivia were helping Ashe, just Tryndamere. I never saw that, do you know the link to it? I'm interested in seeing it

So WW is associated with Urf, but Urf's idol Jax is not? Wha?

Anivia has also formed a bond with Ashe and Nunu.

Quote: Surprisingly, Anivia has struck up a friendship with the yeti of this region - a friendship that grows deeper and deeper with each passing moon. She has formed a close bond with two League champions: Nunu (and Willump) and the nomad princess Ashe.

Master Yi has a strong connection to Warwick or Singed, can't remember which.

They killed his village.