A horse that's buddy sour. We've all dealt with it. Normally the advice you get is to either...
1. Make your horse work and cause it to be difficult near his buddy and then make it easy when he's not around his buddy by letting him rest.
2. Don't let your horse near his buddy. Keep them separated and after a certain amount of time he'll get used to not being around him.
BOTH of those methods work...temporarily.
But the reason horses are buddy sour is because they crave the satisfaction, security and leadership from the other horse.
But, what if instead of having to "fix" a buddy sour issue, your horse naturally got those things from you instead of other horses?
The result is a horse who's buddy sour to you (the human).