• We have updated our Community Code of Conduct. Please read through the new rules for the forum that are an integral part of Paradox Interactive’s User Agreement.
You've raised them to hate you (lots of personality traits conflicting)? Or you have realm duress, or rebelliousness spreading? Dunno... You can bribe him pretty freely, since you'll eventually play as him anyway, and he'll spend the money on province improvements anyway.

Sounds weird though, I thought the first heir gets about +3% loyalty, and close relatives get something like +2% too, so if you're not having any problems with other vassals (low reputation, prestige, realm duress), this shouldn't happen, since the effect of personality traits on loyalty is capped at +-5%.
 
Once you have given him land, check his loyalty. As a courtier he might have gained a very low loyalty and the game remembers his loyalty rating towards you when you give him land of his own.

When you have given him one county, check his loyalty, if it is low then sent him a gift to raise it.
 
Weird, usually heirs are among the most loyal vassals, unless you're a kinslayer. Although I have had my cases of revolting family members, it's not very common.
 
Yeesh. I prefer under two, try quite hard to keep it under 4, and I don't think i've ever gone over 7.5... % loyalty loss per month that is. If you're talking about actual BB, I can't remember the conversion rate at the moment.
 
Maybe my badboy was too high? I always keep it about under 10 though...

I usually try to keep my BB under 2.5%. But did you once sent your heir to became a foster-ling? Maybe along the way your heir pick up a very conflicting traits with your king (e.g. a skeptical king with a zealous heir).
Or maybe simply because your BB is way too high.
 
Maybe my badboy was too high? I always keep it about under 10 though...

10? Geez, usually it's very hard to keep the realm intact when it reaches 5. I rarely go over 4, because usually over 2 means that you have to bribe your vassals constantly so that they won't revolt. It is very expensive if you want to avoid civil war when BB is more than 3 or 4.