For my part I have three family lines, two of which dislike each other and one which is a junior branch so each of them acts differently.
The most powerful military branch of the family fights with everyone, all the time, and holds grudges over nothing at all. I admit that I use some OOC variables, basically until you hit 100 days in game I stretch my mind to come up with ways for any Fraoch to go to the wall for the character, but given that the two main characters are a mercury addict and a religious psycho an excuse can usually be concocted. After 100 days I look for ways to start feuds, as it promotes interactivity, and feuds drove a whole lot of good RP and character development.
I would point out there is a difference between holding a grudge and acting on a grudge, but shaking your fist across a continent is awesome.