Only rumours currently but I'd still hold out at least a while.
To answer your FEC questions:
Long ago Nagash had his most faithful vampire servant, the Bloodrose Prince who for some reason turned against him, Nagash cursed him to look like on the outside how he is on the inside (ugly because he's evil), imprisoned him in a tower full of mirrors for all eternity so he could look at his hideous form. This understandably sent the vampire mad and eventually this madness led to the delusion that things were back to how they were before he turned against Nagash.
Luckily for our crazy Prince, Sigmar attacked Shyish and accidentally freed him. The Bloodrose Prince, now known as the Carrion King, started infecting other vampires who became his followers, they now have the same delusion and also get mutated to look more like their liege but see themselves as benevolent Kings or leaders of great nations. These Abhorrents then draw human cannibals to themselves and these guys share the delusion and mutate into Ghouls and then the Abhorrents (Ghoul Kings and Archregent) make other Ghoul Kings who go off and form their own kingdoms and repeat the cycle of infecting with the delusion.
Not all of them think they're knights as the Blisterkin see themselves as a cult of the sun going about to spread their faith. I think ghouls do get a small glimpse every now and again that somethings not right but it doesn't last long.