Muslim rulers receive relationship bonus with their vassals from both prestige and piety. That means they can (and the big ones like the Fatimids always will) get up to +40 relations with all of their vassals. Add to that bonuses from hajaj (for anyone) and Sayyid (for certain characters, most notably Fatimids) and the result is a permamently stable empire where family is the only possible problem.
Is this WAD?
Is this WAD?