I think you need to research the confederations separately in the tech tree.

I do not see that research in my tree, if so tell me where please. And when I open diplomacy the option to confederate is not there.

Unless Venris changed something lyonese doesn't need researches to confed the other brets and she simply doesn't have them to begin with. That said they are a bit harder to confed because of the lack of a post-research prompt.

Are the factions you're referring to the crusader factions or the ones in bretonnia? If you attack and kill arhkan the black and the vamps above you the game will prompt you into confederating the nearby crusading factions.

https://imgur.com/a/1ttL6EW See this image, I killed arhkan at the beginning and i only confederated once. idk what can be

So i don't believe you can confed crusader factions in diplo, you have to fight and kill the tomb king/vampire factions around you and you will eventually get prompts for them all to join you. At least that's how I remember doing it.

Havn't played repanse in awhile so kinda fuzzy on how it works.

The same thing happened to me recently as well. I was playing Repanse in the vortex campaign, I killed the vampire faction and arkan the black early, but didn't get any confederation prompts. I was only able to confederate one of the factions around turn 80 or so, using the normal deplomacy menu (with me having a much bigger balance of power than they did). After doing some research online I think it's a "feature" (or bug idk) with the vanilla game. People have been saying that if you auto resolve some of the battles, the confederation option won't properly pop up, so I think you have to manually fight the battles to get the confederation prompt.

Thanks both of you, I will try that.

Well, as an update, I played all battles manually and even so I can't confederate with the knights of flame.

Hmmmm I'll run a campaign tonight to test if it's broken on my end too. I remember it being fairly easy to confederate them all with just a handful of battles.

So just did a legendary mortal empires campaign to turn 10 and was able to confed both knights of the flame and knights of origo so confederating them might be buggy but not broken.

This is roughly what I did incase there's other variables involved with procing the confederation prompts:
Turn 1: kill the army nearby, recruit a solo lord, move down and recruit as many of the men at arms with swords as i can.
Turn 2: move 50% downward, encamp, recruit more swordmen.
Turn 3: move down more but stay in territory, encamp, recruit more swords. You should pretty much have a full army at this point.
Turn 4-5: force march repanse army and the solo lord straight to wizard caliphs palace, arkhan always leaves it undefended and he's not at war with you yet. If you can kill beastmen along the way do so.
Turn 6: Take Wizard Caliiph, this is where knights of the flame confed' me.
Turn 7-10 move up to sorcerer's island while staying in encamp to replenish, at some point bait with your solo lord in forced march while repanse is in ambush to kill arkhan and then take the city, taking sorc islands is where knights of origo had confed me.

引用自 Ghilgamesch：

So just did a legendary mortal empires campaign to turn 10 and was able to confed both knights of the flame and knights of origo so confederating them might be buggy but not broken.

This is roughly what I did incase there's other variables involved with procing the confederation prompts:
Turn 1: kill the army nearby, recruit a solo lord, move down and recruit as many of the men at arms with swords as i can.
Turn 2: move 50% downward, encamp, recruit more swordmen.
Turn 3: move down more but stay in territory, encamp, recruit more swords. You should pretty much have a full army at this point.
Turn 4-5: force march repanse army and the solo lord straight to wizard caliphs palace, arkhan always leaves it undefended and he's not at war with you yet. If you can kill beastmen along the way do so.
Turn 6: Take Wizard Caliiph, this is where knights of the flame confed' me.
Turn 7-10 move up to sorcerer's island while staying in encamp to replenish, at some point bait with your solo lord in forced march while repanse is in ambush to kill arkhan and then take the city, taking sorc islands is where knights of origo had confed me.

I will try that, thanks man